North Korea on Wednesday barred South Korean workers from entering a jointly run factory park just over the heavily armed border in the North, officials in Seoul said, a day after Pyongyang announced it would restart its long-shuttered plutonium reactor and increase production of nuclear weapons material. 
 
 South Korean army soldiers walk on the empty road after South Korean vehicles which were refused for entry to North Korea at the customs, immigration and quarantine office in Paju, South Korea, near the... (Associated Press) 
 
 South Korean vehicles turn back their way as they were refused for entry to North Korea's city of Kaesong, at the customs, immigration and quarantine office in Paju, South Korea, near the border village... (Associated Press) 
 
 South Korean Marine K-55 self-propelled howitzers are on positions during an exercise against possible attacks by North Korea near the border village of Panmunjom in Paju, South Korea, Wednesday, April... (Associated Press) 
 
 South Korean vehicles turn back their way as they were refused for entry to North Korea's city of Kaesong, at the customs, immigration and quarantine office in Paju, South Korea, near the border village... (Associated Press) 
 
 South Korean Marines pass by K-55 self-propelled howitzers during an exercise against possible attacks by North Korea near the border village of Panmunjom in Paju, South Korea, Wednesday, April 3, 2013.... (Associated Press) 
 
 The move to block South Koreans from going to their jobs at the Kaesong industrial complex, the last remaining symbol of detente between the rivals, comes amid increasing hostility from Pyongyang, which has threatened to stage nuclear and missile strikes on Seoul and Washington and has said that the armistice ending the 1950s Korean War is void. 
 
 Seoul's Unification Ministry spokesman Kim Hyung-suk said Pyongyang was allowing South Koreans to return home from Kaesong. Three workers returned Wednesday morning; dozens more were scheduled to return later. But Kim said about 480 South Koreans who had planned to travel to the park Wednesday were being refused entry. 
 
 North Korean authorities cited recent political circumstances on the Korean Peninsula when they delivered their decision to block South Korean workers from entering Kaesong, Kim said without elaborating. 
 
 It's the latest sign of deepening tensions on the Korean Peninsula. North Korea said Tuesday that it will quickly begin "readjusting and restarting" the facilities at its main Nyongbyon nuclear complex, including the plutonium reactor and a uranium enrichment plant. Both could produce fuel for nuclear weapons. Analysts saw the statement as Pyongyang's latest attempt to extract U.S. concessions by raising fears of war. Experts estimate reactivating the reactor could take anywhere from three months to a year. 
 
 The rising tide of threats in recent weeks are seen as efforts by the North to force new policies in Seoul, diplomatic talks with Washington and to increase domestic loyalty to young North Korean leader Kim Jong Un by portraying him as a powerful military commander. 
 
 North Korea is angry about ongoing South Korea-U.S. military drills and new U.N. sanctions over its Feb. 12 nuclear test, its third. The Korean Peninsula technically remains in a state of war because a truce, not a peace treaty, ended the Korean War. The United States stations 28,500 troops in South Korea as a deterrent to North Korea. 
 
 The North's plutonium reactor began operations in 1986 but was shut down as part of international nuclear disarmament talks in 2007 that have since stalled. Tuesday's nuclear announcement underscores worries about North Korea's timetable for building a nuclear-tipped missile that can reach the United States, although it is still believed to be years away from developing that technology. 
 
 The North's rising rhetoric has been met by a display of U.S. military strength, including flights of nuclear-capable bombers and stealth jets at the annual South Korean-U.S. military drills that the allies call routine but that North Korea claims are invasion preparations. 
 
 The Kaesong industrial park started producing goods in 2004 and has been an unusual point of cooperation in an otherwise hostile relationship between the Koreas. 
 
 North and South Korea do not allow their citizens to travel to the other country without approval, but an exception had previously been made each day for the South Koreans working at Kaesong. 
 
 About 120 South Korean firms run factories in the border town of Kaesong, with 53,000 North Koreans working there. Using North Korea's cheap, efficient labor, the Kaesong complex produced $470 million worth of goods last year. 
 
 Pyongyang threatened last week to shut down the park, which is run with mostly North Korean labor and South Korean know-how. It expressed anger over South Korean media reports that said North Korea hadn't yet shut the park because it is a source of crucial hard currency for the impoverished country. 
 
 In 2009, North Korea closed its border gate in anger over U.S.-South Korean military drills, leaving hundreds of South Korean workers stranded in Kaesong for several days. The park later resumed normal operations. 
 
 "I feel worried that I'm unable to do business and also feel anxious," Joe In-suk, a 54-year-old South Korean who had planned to travel to Kaesong on Wednesday, said at a border checkpoint in Paju, South Korea. About a dozen South Korean trucks were lined up at the checkpoint leading into North Korea. 
 
 If North Korea continues to deny entrance to South Korean workers, it could be tantamount to a shutdown because Kaesong factories cannot operate production lines without supplies of raw materials sent regularly by truck from the South to the North. 
 
 A South Korean manager whose company runs a factory in Kaesong was worried that buyers would drop future orders if North Korea continued to block workers and supplies from the South. 
 
 "For some companies, today's move must have already dealt them a blow," the manager said Wednesday, speaking on condition of anonymity because he wasn't authorized to talk to the media. "We cannot produce goods without raw material." 
 
 Seoul's Unification Ministry urged Pyongyang to "immediately normalize" cross-border traffic in and out of Kaesong. 
 
 The U.S., meanwhile, called for North Korea to abandon its nuclear ambitions, saying it would be "extremely alarming" if Pyongyang follows through on a vow to restart its plutonium reactor. 
 
 White House spokesman Jay Carney said the U.S. is taking steps to ensure it has the capacity to defend itself and its allies. 
 
 But Carney noted that a string of threats from North Korea toward the U.S. and South Korea so far have not been backed up by action, calling the threats part of a counterproductive pattern. He called on Russia and China, two countries he said have influence on North Korea, to use that influence to persuade the North to change course. 
 
 U.S. Defense Secretary Chuck Hagel called North Korea's development of nuclear weapons a growing threat. In a telephone call Tuesday evening to Chinese Defense Minister Chang Wanquan, Hagel said Washington and Beijing should continue to cooperate on North Korea's pursuit of nuclear weapons and ballistic missiles. 
 
 China, North Korea's only major economic and diplomatic supporter, expressed unusual disappointment with its ally. 
 
 Hwang Jihwan, a North Korea expert at the University of Seoul, said the North "is keeping tension and crisis alive to raise stakes ahead of possible future talks with the United States." 
 
 "North Korea is asking the world, `What are you going to do about this?'" he said. 
 
 The North's nuclear statement Tuesday suggests it will do more to produce highly enriched uranium. The technology needed to make highly enriched uranium bombs is much easier to hide than huge plutonium facilities. North Korea previously insisted that its uranium enrichment was for producing electricity _ meaning low-enriched uranium. 
 
 Kim Jin Moo, a North Korea expert at the Korea Institute for Defense Analyses in South Korea, said that by announcing it is "readjusting" all nuclear facilities, including the uranium enrichment plant, North Korea "is blackmailing the international community by suggesting that it will now produce weapons-grade, highly enriched uranium." 
 
 The North's plutonium reactor was disabled under a 2007 deal made at now-dormant aid-for-disarmament negotiations involving the North, the U.S., South Korea, Japan, China and Russia. 
 
 In 2008, North Korea destroyed the cooling tower at Nyongbyon in a show of commitment, but the deal later stalled after the North balked at allowing intensive international fact-checking of its past nuclear activities. North Korea pulled out of the talks after condemnation of its long-range rocket launch in April 2009. 
 
 North Korea is believed to have exploded plutonium devices in its first two nuclear tests, in 2006 and 2009. 
 
 There had long been claims by the U.S. and others that North Korea was also pursuing a secret uranium program. In 2010, the North unveiled to visiting Americans a uranium enrichment program at Nyongbyon. 
 
 Analysts say they don't believe North Korea currently has mastered the miniaturization technology needed to build a warhead that can be mounted on a missile, and the extent of its uranium enrichment efforts is also unclear. Some experts estimate North Korea may have enough plutonium for perhaps four to eight rudimentary bombs. 
 
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 Associated Press writers Foster Klug, Hyung-jin Kim and Youkyung Lee in Seoul and Kim Yong-ho in Paju contributed to this report. 
 
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 Follow Foster Klug on Twitter at twitter.com/APKlug; Sam Kim at twitter.com/samkim_ap; Youkyung Lee at twitter.com/YKLeeAP ||||| South Korean vehicles, transporting both South Korean employees working at North Korea's Kaesong Industrial Complex (KIC) and products made in KIC, head towards the South's Customs, Immigration and Quarantine (CIQ), just south of the demilitarised zone separating the two... 
 
 PAJU, South Korea Hundreds of South Koreans rejected the chance to leave factories in North Korea on Thursday that have become the center of a bitter standoff between the two countries, running the risk of becoming hostages to keep their plants going. 
 
 For those whose commute to work already involved a trip across the world's most heavily fortified border and into one of its most repressive states, this week's tensions were another reminder of their precarious livelihoods. 
 
 It also showed how South Koreans have become largely inured to threats from their impoverished and bellicose neighbor. 
 
 On Wednesday, Pyongyang barred access to the Kaesong Industrial park, where 123 mostly small South Korean firms employ 50,000 North Korean workers to make clothing, shoes and other goods. 
 
 "I have four dependents in my family. We didn't go there for political reasons, we were there to make our living," said Kwon Bo-sun, a 44-year-old trailer driver who was waiting at the South Korean border town of Paju to see if he would be allowed to truck supplies into the zone. 
 
 Pyongyang has allowed South Korean factory managers and workers to leave Kaesong, about 5 km (3 miles) inside North Korea. 
 
 But out of 828 people who spent the night there just 222 had indicated they wanted to return to South Korea on Thursday, with the rest continuing to try to keep their factories running. 
 
 Many South Koreans waited all day on Thursday at Paju, hoping to get in. Some expressed concern that a cut in gas supplies would affect the operation of equipment at their factories. One worker who returned asked reporters not to sensationalize the standoff. 
 
 The companies are estimated to have invested around $500 million in the park since it was inaugurated in 2000. 
 
 South Korean corporate giants such as Samsung Electronics and Hyundai Motor, the sort of companies that could sustain losses from the park's closure, do not have operations in Kaesong. 
 
 The North warned again on Thursday that it would close the zone in reprisal for what it sees as "hostile" military exercises by the United States and South Korea which have been beefed up in response to Pyongyang's threats of war. 
 
 Many South Koreans are used to the rhetoric from North Korea, which remains technically at war with both the South and with the United States after an armistice rather than a peace treaty ended the 1950-53 Korean conflict. 
 
 North Korea has now staged three nuclear weapons tests, the most recent in February, which drew new sanctions from the United Nations. 
 
 It shelled a South Korean island in 2010 and is blamed for killing 46 South Korean sailors when a naval vessel was torpedoed in the same year. 
 
 Pyongyang has in the past also launched commando raids, tried to kill South Korean presidents, bombed an airliner and killed South Korean government officials in a bombing overseas. 
 
 "It is true most people involved in Kaesong do not have that sense of urgent risk to their personal safety," said a business executive with operations there who declined to be identified for fear his business could be affected. 
 
 KAESONG, A BAROMETER OF FAITH IN UNITED KOREA 
 
 The economic zone generates $2 billion a year in trade and pays an average $130 a month in wages to North Koreans who might otherwise struggle to find a job in an economy that has shrunk over the past 20 years. 
 
 It is also practically the last vestige of the "Sunshine Policy" of rapprochement between the two Koreas and a powerful symbol that the divided country could one day reunify. 
 
 Even as North Korea's propaganda machine hurled more insults at Seoul on Thursday, it appeared that a sense of solidarity between Koreans in the zone was still holding. 
 
 "When food supplies come in from the North, (they are) sharing some with the South Korean workers there," said Park Yun-kyu, an executive. 
 
 Most food supplies are usually shipped in from South Korea, which has not happened now for two days. 
 
 Other South Koreans who have been in the zone said North Korean workers had been less friendly this week. 
 
 There were brief jitters in Seoul's financial markets when one South Korean businessman said the North would close the zone on April 10. 
 
 The South's Unification Ministry, which handles inter-Korean relations, denied the reports and said the North wanted to be told of scheduled plans for workers leaving over the next week. 
 
 "The North's request to several companies for a schedule of people returning to the South by April 10 has been distorted to say the North had requested a total pullout," the ministry said. 
 
 South Korea has had to submit a list of those wishing entry to the complex three days in advance. 
 
 North Korea itself has not issued a statement on restricting entry but on Thursday again threatened permanent closure if Seoul continued to offend a country that bridles at even the mildest criticism. 
 
 "If the South's puppet conservative group and its media continue bad-mouthing ... we will be taking the stern measure of pulling out all of our workers from the Kaesong industrial zone," its KCNA news agency said. 
 
 (Additional reporting by Christine Kim; Editing by Dean Yates) ||||| The top South Korean official charged with handling North-South relations says the time has come for South Korean workers still at the shuttered Kaesong factory zone to return home. 
 
 
 
 Unification Minister Ryoo Kihl-jae said Friday that the government has made an "unavoidable decision" to bring about 180 South Korean workers home. 
 
 
 
 The decision came hours after North Korea rejected the South's proposal for formal negotiations to restart operations at the Kaesong complex. 
 
 
 
 Seoul gave Pyongyang 24 hours on Thursday to agree to talks, warning of a tough response if Pyongyang did not agree to the offer. 
 
 
 
 Hours after the deadline passed Friday, Pyongyang dismissed the offer and warned that it would be the first to take tough action if the South insists on worsening the situation at the border town. 
 
 
 
 South Korean President Park Geun-hye met with her security-related Cabinet ministers on Friday, regarding fate of the Kaesong complex. 
 
 
 
 
 
 
 
 Operations at Kaesong, just north of the border, have been suspended since North Korea angrily pulled its workers and blocked South Korean access to the center earlier this month. 
 
 
 
 About 180 South Koreans remain there in hopes that production can resume, but they are thought to be quickly running out of food and supplies. 
 
 
 
 Kaesong is the last remaining symbol of cooperation between the two foes, and is seen as a bellwether of Korean relations. Although work at the center has been suspended during times of heightened tensions, it has never been shut down completely since it was established in 2004. 
 
 
 
 Though Pyongyang has refrained from making daily threats of violence against the South in recent days, tensions remain high on the Korean peninsula. 
 
 
 
 North Korea is angry over U.N. Security Council sanctions passed in response to Pyongyang's February nuclear test, as well as annual joint military exercises between South Korea and the United States.
– Some action from North Korea after weeks of harsh words: Pyongyang has blocked nearly 500 South Korean workers from entering a jointly run factory park just over the heavily armed border in the North today. As Reuters reports, the move to block South Koreans from going to their jobs at the Kaesong Industrial Park, dubbed the "last remaining symbol of detente" between the rivals by the AP, puts a vital source of revenue for the North at risk. As such, some South Korean experts believe the move could be a short-lived one. And signs suggest the factories haven't been shuttered: Though the North has given the OK for the 861 South Koreans working in the zone to travel home, as of today fewer than 40 had done so, reports the New York Times. However, Reuters notes that the South transports all supplies to the complex, so food stocks could begin to dwindle. Entry to the park, which is home to 123 factories, was previously blocked three times in 2009, once for a three-day period. The move comes amid increasing hostility from Pyongyang, include yesterday's threat to restart its sole nuclear reactor.