A protester wearing a jacket with "No THAAD" letters, participates during a rally to oppose the plan to deploy the Terminal High-Altitude Area Defense system, or THAAD, in front of the Defense Ministry... (Associated Press) 
 
 SEOUL, South Korea (AP) — U.S. missile launchers and other equipment needed to set up a controversial missile defense system have arrived in South Korea, the U.S. and South Korean militaries said Tuesday, a day after North Korea test-launched four ballistic missiles into the ocean near Japan. 
 
 The plans to deploy the Terminal High-Altitude Area Defense system, or THAAD, within this year have angered not only North Korea, but also China and Russia, which see the system's powerful radars as a security threat. 
 
 China responded quickly, saying it will take "necessary measures" to protect itself and warning that the U.S. and South Korea should be prepared to bear the consequences. 
 
 Washington and Seoul say the system is defensive and not meant to be a threat to Beijing or Moscow. The U.S. military said in a statement that THAAD can intercept and destroy short and medium range ballistic missiles during the last part of their flights. 
 
 "Continued provocative actions by North Korea, to include yesterday's launch of multiple missiles, only confirm the prudence of our alliance decision last year to deploy THAAD to South Korea," Adm. Harry Harris, head of the U.S. Pacific Command, said in the statement. 
 
 Some South Korean liberal presidential candidates have said that the security benefits of having THAAD would be curtailed by worsened relations with neighbors China and Russia. 
 
 "China firmly opposes the deployment of THAAD," Chinese Foreign Ministry spokesman Geng Shuang said at a regular briefing Tuesday. "We will definitely be taking necessary measures to safeguard our own security interest. All consequences entailed from that will be borne by the U.S. and (South Korea). We once again strongly urge the relevant sides to stop the process of deployment and refrain from going further down that wrong path." 
 
 China's condemnation of South Korea's plans to deploy THAAD has triggered protests against a South Korean retail giant, Lotte, which agreed to provide one of its golf courses in southern South Korea as the site of THAAD. The South Korean government also raised concerns about a reported ban on Chinese tour groups visiting the country. 
 
 On Tuesday, China's Global Times, an outspoken nationalist tabloid published by the ruling Communist Party's flagship People's Daily, criticized North Korea over the missiles. 
 
 "By firing four missiles at once this time, the military confrontation between Pyongyang, Seoul and Washington escalates a notch," the paper said. "Noticeably, the Chinese public is angry that Pyongyang's nuclear program has provided an excuse for Seoul to deploy THAAD." 
 
 An official from South Korea's Defense Ministry, who didn't want to be named, citing office rules, said that the equipment that arrived in South Korea included launchers, but didn't confirm how many. 
 
 While South Korea's media speculate that the THAAD deployment could be completed by as early as April, the ministry official couldn't confirm those reports. The official said that the plan was to have the system operational as soon as possible. 
 
 On Monday, North Korea fired four ballistic missiles in an apparent protest against ongoing U.S.-South Korean military drills that it views as an invasion rehearsal. The missiles flew about 1,000 kilometers (620 miles) on average, three of them landing in waters that Japan claims as its exclusive economic zone, according to South Korean and Japanese officials. 
 
 The North's state media on Tuesday said leader Kim Jong Un supervised a ballistic rocket launching drill, a likely reference to the four launches reported by Seoul and Tokyo. Involved in the drills were artillery units tasked with striking "U.S. imperialist aggressor forces in Japan," according to the Korean Central News Agency. 
 
 There was pride and defiance among the elite citizens who live in North Korea's showcase capital, Pyongyang. 
 
 "If the U.S. imperialists and their South Korean puppets shoot even just one spark into our sovereign territory, we will completely destroy those aggressors, without any mercy, with our invincible Hwasong artillery, which are loaded with nuclear warheads," Sim Chol Su, echoing the propaganda often found in state media, told The Associated Press. 
 
 North Korea uses "Hwasong" to describe a broad range of its ballistic missiles, including Scuds and the mid-range missiles that are referred to as Rodong and Musudan by outside analysts. 
 
 South Korea's Joint Chiefs of Staff said that the missiles fired by the North were believed to be "improved versions" of Scud missiles. South Korean experts say North Korea's extended-range Scuds and mid-range Rodong missiles are capable of hitting Japan, including U.S. military bases in Okinawa. 
 
 Kim "ordered the KPA (Korean People's Army) Strategic Force to keep highly alert as required by the grim situation in which an actual war may break out anytime," a KCNA dispatch said. 
 
 ___ 
 
 Associated Press writers Chris Bodeen and Gillian Wong in Beijing contributed to this report. ||||| Image copyright Reuters Image caption The defence system will take out any missiles considered a threat to South Korea 
 
 The US says it has begun deploying the first parts of a controversial missile defence system in South Korea. 
 
 The Terminal High-Altitude Area Defense system (Thaad) is designed to protect against threats from North Korea. 
 
 The move to begin installing the system comes a day after the North launched four ballistic missiles, breaking international sanctions. 
 
 But the US-South Korean arrangement has angered many on the Korean peninsula and around the region, including China. 
 
 South Korean media said operations to install a Thaad battery had begun on Monday, with some parts flown from the US to an air base near Seoul. A statement from the US military confirmed that the "first elements" of the system had been sent to South Korea. 
 
 South Korea's Yonhap news agency, quoting a military official, said the system could be operational "as early as April". 
 
 Chinese foreign spokesman Geng Shuang said on Tuesday that China opposed the deployment and would "resolutely take necessary measures to defend our own security interests". 
 
 What is the Terminal High Altitude Area Defense System (Thaad)? 
 
 Shoots down short and medium-range ballistic missiles in the terminal phase of their flight 
 
 Uses hit-to-kill technology - where kinetic energy destroys the incoming warhead 
 
 Has a range of 200km and can reach an altitude of 150km 
 
 US has previously deployed it in Guam and Hawaii as a measure against potential attacks from North Korea 
 
 What impact will S Korea's expanded missile defence system have? 
 
 1. The enemy launches a missile 
 
 2. The Thaad radar system detects the launch, which is relayed to command and control 
 
 3. Thaad command and control instructs the launch of an interceptor missile 
 
 4. The interceptor missile is fired at the enemy projectile 
 
 5. The enemy projectile is destroyed in the terminal phase of flight 
 
 The launcher trucks can hold up to eight interceptor missiles. 
 
 But the deployment is controversial? 
 
 There is domestic opposition - many South Koreans believe the defence system will itself become a target, endangering people who live around the military sites. Opponents have staged multiple demonstrations. 
 
 Internationally, both China and Russia have raised concerns, saying the system could affect the regional security balance. 
 
 Last year, China's foreign minister said the system went "far beyond" the defence needs of the Korean peninsula. Russia's envoy to Seoul has called it a "direct threat" to national security. 
 
 So why is China worried? By Jonathan Marcus, BBC News defence correspondent 
 
 The Thaad system is well-suited to defend South Korean targets against relatively limited range North Korean missiles. But it has no ability to intercept Chinese inter-continental ballistic missiles that target the US. Why then is China so annoyed? 
 
 What concerns Beijing is the system's powerful X-band radars that can "reach" far into Chinese territory. The Chinese military worries that these could be used to spot Chinese missile launches and feed the data to cue up other US defensive systems, eg interceptor missiles based in the US, potentially affecting China's deterrent capability. 
 
 But the US already has powerful radars based in Japan and a Thaad system in Guam. It's not easy to quantify the additional benefit that Thaad radars in South Korea would give the Pentagon. But they will certainly give the South Koreans an important and expanded new layer of defence against missile attack. 
 
 What happened in the latest missile launch? 
 
 North Korea threatened last week to fire missiles in response to the start of the Foal Eagle US-South Korean military exercises. The annual drills infuriate the North, which sees them as preparation for an invasion from the South. 
 
 Then early on Monday, it fired four missiles from the Tongchang-ri region, near the border with China. 
 
 Three of the projectiles flew some 1,000km (620 miles) and fell into Japan's exclusive economic zone (EEZ). The exact type of missile is not yet clear but South Korean officials said they appeared to be an upgraded version of a Scud missile. 
 
 What was the international reaction? 
 
 The US and Japanese leaders held phone discussions after the missile launch and the United Nations Security Council is due to meet on Wednesday in an emergency meeting requested by the US and Japan to discuss the incident. 
 
 Admiral Harry Harris, commander of the US South Pacific Command, said the launch confirmed "the prudence" of the decision to deploy Thaad. 
 
 But the deployment will likely worsen tensions between Seoul and Beijing. In recent days South Korea has accused China of economic retaliation linked to Thaad in areas, including tourism and air travel. 
 
 There has also been an outpouring of anger by Chinese consumers against the South Korean retailer Lotte, which allowed Thaad to be installed on one of its sites. Several of Lotte's stores in China have been closed down suddenly. Beijing rejects claims of economic retaliation. 
 
 Is China retaliating against Lotte missile deal?
– US missile launchers and other equipment needed to set up a controversial missile defense system have arrived in South Korea, the US and South Korean militaries said Tuesday, a day after North Korea test-launched four ballistic missiles into the ocean near Japan. The plans to deploy the Terminal High-Altitude Area Defense system, or THAAD, within this year have angered not only North Korea, but also China and Russia, which see the system's powerful radars as a security threat, the AP reports. China firmly opposes the deployment and it responded quickly, saying it will take "necessary measures" to protect itself and warning that the US and South Korea should be prepared to bear the consequences. Washington and Seoul say the system is defensive and not meant to be a threat to Beijing or Moscow. The US military said in a statement that THAAD can intercept and destroy short and medium range ballistic missiles during the last part of their flights. "Continued provocative actions by North Korea, to include yesterday's launch of multiple missiles, only confirm the prudence of our alliance decision last year to deploy THAAD to South Korea," Adm. Harry Harris, head of the US Pacific Command, said in the statement. The BBC reports that there is also opposition within South Korea, with those living near missile sites fearing that the system itself could become a target.