Story highlights "It's dozens and dozens, scores of casualties," the head of the U.N. Security Council says 
 
 About 15,000 to 20,000 civilians have fled to United Nations bases in the city, he says 
 
 State Department says U.S. Embassy suspending normal operations until further notice 
 
 Sporadic gunfire still rattling Juba, diplomats say 
 
 The death toll from violence in South Sudan is "heavy," the United Nations said Tuesday, and thousands of people have sought refuge in the organization's compounds in Juba. 
 
 Gunfire rang out again in the capital of in Africa's newest nation just hours after the country's President said his forces had halted a coup attempt. 
 
 Clashes, which began on Sunday evening, have left hundreds in urgent need of medical care, the International Committee of the Red Cross (ICRC) said. 
 
 Gerard Araud, the French representative to the United Nations and the current President of the Security Council, said precise figures on the death toll weren't available. 
 
 "But it's heavy," he said. "It's dozens and dozens, scores of casualties, it's really not a minor incident." 
 
 Officials at the United Nations are "extremely concerned" about the violence, Araud said, due to the high number of casualties and because the fighting appears to be between different ethnic groups in South Sudan. 
 
 On Tuesday, sporadic gunshots were heard in the area of Tonping, the U.S. Embassy said on its Twitter feed, quoting U.N. radio. It recommended that U.S. citizens currently in the country depart immediately. 
 
 Women and children carrying bags, kettles, pots and basic belongings arriving at a U.N compound to seek shelter could be seen in pictures posted on the U.N. mission in South Sudan (UNMISS) Facebook page. 
 
 Araud said Tuesday evening that around 15,000 to 20,000 civilians were taking refuge in the two UNMISS compounds in Juba, putting a strain on supplies of medicine, food, water and security resources. 
 
 In a televised address Monday, South Sudan President Salva Kiir blamed soldiers loyal to his sacked deputy Riek Machar for starting the fighting Sunday evening. 
 
 Dressed in fatigues, he said the government was in full control of the capital and announced a nighttime curfew. 
 
 Ten people were arrested in connection with the foiled coup, according to a statement posted Tuesday on the South Sudan government website. 
 
 Hundreds in need of medical care 
 
 The ICRC said it was providing Juba's two major hospitals with support, such as wound-dressing materials, to cope with the heavy influx of patients. 
 
 More than 300 people have been admitted to Juba Teaching Hospital and Juba Military Hospital over the past two days, it said. 
 
 "We know there are more people who need care, but they are having difficulty reaching healthcare facilities because of the security situation and the lack of available transportation," Felicity Gapes, an ICRC delegate leading the medical response on the ground, said in a statement. 
 
 "Staff in both hospitals have been working around the clock, but they are struggling because of the sheer volume of patients and the severity of the injuries." 
 
 The United Nations said Secretary-General Ban Ki-moon spoke with Kiir by phone Tuesday, expressing his concern about the fighting. 
 
 He urged "all parties to cease hostilities immediately, and called on the government to exercise restraint in the management of the situation and to guarantee the protection of all civilians regardless of their ethnicities." 
 
 Deep-running tensions 
 
 Kiir's dismissal of his Cabinet in July further inflamed deep tensions between his Dinka community and Machar's Nuer community. 
 
 South Sudan formally split from Sudan in 2011 following a referendum, after decades of conflict. Numerous armed groups remain active in the oil-rich country. 
 
 UNMISS said Hilde F. Johnson, special representative of the U.N. secretary-general, called on "all parties in the current situation to refrain from any community-motivated violence." 
 
 "At a time when unity among South Sudanese is more needed than ever, I call on the leaders of this new country and all political factions and parties, as well as community leaders to refrain from any action that fuels ethnic tensions and exacerbates violence," Johnson said. 
 
 Juba's international airport remained closed. And with phone networks sketchy, embassies were turning to social media to stay in touch with their citizens, mainly calling on them to stay home and avoid unnecessary movement. 
 
 The State Department said U.S. citizens currently in South Sudan should leave immediately, and it ordered the departure of non-emergency U.S. government personnel from the country. 
 
 "The Embassy is also suspending normal operations until further notice and cannot provide routine consular services to U.S. citizens in South Sudan," it said. 
 
 The African Union said it was "deeply concerned" about the events in South Sudan, urging the government, leadership and other stakeholders to exercise maximum restraint and avert any further escalation. ||||| Fresh clashes have broken out in the South Sudanese capital Juba, and at least 66 soldiers have been killed, a day after President Salva Kiir said security forces had put down an attempted coup by supporters of his former deputy. 
 
 The US embassy said on its Twitter account late on Tuesday that that all of its citizens in the country should "depart immediately". The account tweeted that it would outline evacuation options on Wednesday morning. 
 
 "So far we have lost seven soldiers who died while they were waiting for medical attention and a further 59 who were killed outside," doctor Ajak Bullen said on the local Radio Miraya. 
 
 Poor communications in Juba, where the mobile phone system has not operated since Monday evening, meant it was difficult to obtain a broad picture of the number of dead during the clashes, which have involved heavy arms and artillery. 
 
 
 
 Kiir said on Monday the fighting between army factions was a bid to seize power by the former vice president, Riek Machar, whom he sacked in July. 
 
 The two men, from different ethnic groups, which have clashed in the past, have long been political rivals. Analysts said divisions between them run deep and rivalries in army ranks have long simmmered. 
 
 Al Jazeera's Rawya Rageh, reporting from neighbouring Nairobi, spoke to South Sudan's Information Minister Michael Makuei Lueth who confirmed at least 10 very senior former government officials have been arrested, including six cabinet ministers. The government named the men on its website. 
 
 There are conflicting reports about the whereabouts of Riek Machar. The government claims he is on his way to Unity State, whereas Machar's spokesperson said he is in fine condition and "very much still in Juba", Rageh said. 
 
 Heavy weapons 
 
 Gunfire - including the sporadic firing of heavy weapons - resumed in the early hours of Tuesday and was still audible at 9am (0600 GMT). It appeared to come from a military headquarters, a few kilometres from the centre of town. 
 
 Residents near Juba airport, which has been closed since Monday, were woken before dawn by gunshots and blasts, a UN worker said. Others also reported bouts of shooting. 
 
 The streets of Juba were deserted, with only military vehicles to be seen and civilians barricaded in their homes. 
 
 Kiir had said in a statement on Monday that security forces had regained control, although a dawn-to-dusk curfew had been imposed. 
 
 "The attackers went and [the] armed forces are pursuing them," Kiir said. "I promise you today that justice will prevail." 
 
 Details of the claimed coup remained sketchy, but South Sudan's Foreign Minister Barnaba Marial Benjamin told the Associated Press news agency that troops in the main army base raided a weapons store in Juba but were repulsed. 
 
 Civilians take refuge 
 
 The UN deputy special representative for South Sudan, Toby Lanzer, told Al Jazeera on Tuesday that about 16,000 civilians were now taking refuge from the fighting in two UN compounds. 
 
 "We will of course do everything we can do protect people. Many people who are coming require health care of all types," he said. 
 
 "Some people have been injured. We've got challenges of a variety - and the water and sanitation situation is also something that we are grappling with." 
 
 Tension had been mounting in South Sudan since Kiir's sacking of Machar. The men belong to different ethnic groups - Kiir to the Dinka, the most powerful, and Machar to the Nuer, but it is not clear whether this latest tension is due to ethnic or political divisions. 
 
 Machar, who has expressed a willingness to contest the presidency in 2015, told Al Jazeera in July that if the country is to be united it cannot tolerate "one man's rule or it cannot tolerate dictatorship." 
 
 His sacking, part of a wider dismissal of the entire cabinet by Kiir, had followed reports of a power struggle within the ruling party. 
 
 South Sudan's government has struggled to create a functioning state since it declared independence from Sudan in 2011 after years conflict with Khartoum during a war that often saw south-south clashes. ||||| (CNN) -- All Americans who presented themselves at the United Nations camp in Bor, South Sudan, were evacuated safely Sunday amid deadly violence in the country, the State Department said. A State Department official said about 15 Americans were flown out. 
 
 U.S. personnel are working to confirm that no other U.S. citizens remain in Bor in need of evacuation, a State Department official said. 
 
 "This morning, the United States -- in coordination with the United Nations and in consultation with the South Sudanese government -- safely evacuated American citizens from Bor, South Sudan," State Department spokeswoman Jen Psaki said in a statement. "U.S. citizens and citizens from our partner nations were flown from Bor to Juba on U.N. and U.S. civilian helicopters. The United States and the United Nations, which has the lead for securing Bor airport in South Sudan, took steps to ensure fighting factions were aware these flights were a humanitarian mission." 
 
 "The U.S. government is doing everything possible to ensure the safety and security of United States citizens in South Sudan. We are working with our allies around the world to connect with and evacuate U.S. citizens as quickly and safely as possible," Psaki said. 
 
 The United Nations moved noncritical staff out of South Sudan's capital, Juba, across the border into Uganda on Sunday, as the violence spread inside the world's newest country. 
 
 U.N. civilian staff were moved from a compound in the flashpoint town of Bor to Juba on Saturday, the same day a U.S. mission to airlift Americans out was aborted when the aircraft came under fire. 
 
 U.S. President Barack Obama said in a letter to congressional leaders Sunday that 46 U.S. service members took part in the mission, and he noted he "may take further action to support the security of U.S. citizens, personnel and property, including our Embassy, in South Sudan." 
 
 Four U.S. troops were wounded in the attack in Bor and were expected to be moved to the U.S. military hospital at Landstuhl, Germany, a senior U.S. official told CNN earlier Sunday. 
 
 One of the injured "went through some pretty serious surgery" after being taken to Nairobi, Kenya, for wounds from the gunshots fired at the aircraft. All four have been able to speak to their families. 
 
 Thousands displaced 
 
 Hundreds of people have been killed in a week of fighting, which has spread from Juba to oil fields farther north. 
 
 South Sudanese President Salva Kiir blamed soldiers loyal to his former vice president, Riek Machar, for starting the violence. 
 
 Up to 40,000 civilians have taken refuge in United Nations bases in the country, Secretary-General Ban Ki-moon said Sunday. 
 
 "There are many more thousands of people who are very much in fear and vulnerable, and at this time, the priority of the United Nations is to (protect) the lives of civilians," Ban told a news conference in the Philippines. 
 
 The U.N. Office for the Coordination of Humanitarian Affairs estimates some 62,000 people have been displaced in total, with five of South Sudan's ten states affected by the violence. 
 
 The U.N. has said some 20 people were killed during an attack Thursday by about 2,000 armed youths on a U.N. peacekeeping base in Jonglei state. Two Indian peacekeepers were also killed. 
 
 After the attack, the assailants fled with arms, ammunition and other supplies, the U.N. said. 
 
 'We will not be intimidated' 
 
 In a statement Sunday, the U.N. said it had made the decision to relocate noncritical staff from Juba to Entebbe, Uganda, as "a precautionary measure to reduce pressures on its limited resources," while still providing assistance and shelter to more than 20,000 civilians who have gathered at its compounds in the capital. 
 
 The U.N. Mission in South Sudan is planning to reinforce its military presence in Bor and Pariang, the organization said. Plans are also under way to relocate all noncritical staff from the U.N. compound near Bentiu in Unity state, and reinforcements will also be sent in. 
 
 "We are not abandoning South Sudan. We are here to stay, and will carry on in our collective resolve to work with and for the people of South Sudan," U.N. envoy Hilde F. Johnson said in the statement. "To anyone who wants to threaten us, attack us or put obstacles in our way, our message remains loud and clear: we will not be intimidated." 
 
 Ban said the U.N. would "transfer our assets from other peacekeeping missions," such as the one in the Democratic Republic of Congo and other areas, to the troubled country. 
 
 "We also seeking support from other key countries who can provide the necessary assets," he said. "We are in shortage of capacity. When the United Nations compound was overrun by 2,000 armed elements, we were having difficulties." 
 
 Echoing calls from Western governments, Ban urged an end to the violence and called on Kiir and Machar "to come to the table and find a political way out of this crisis." 
 
 "They are responsible to the people of South Sudan to end the crisis and find the political means of addressing their differences," he said. 
 
 Ban said he had dispatched a special representative to Juba to work with the U.N. envoy in the city. Washington is also sending an envoy. 
 
 Tensions have been high in South Sudan since July, when Kiir dismissed Machar and the rest of the Cabinet. The move inflamed tensions between Kiir's Dinka community and Machar's Nuer community. 
 
 South Sudan formally split from Sudan in 2011 after a referendum, following decades of conflict. Numerous armed groups remain active in the oil-rich country. 
 
 CNN's Anna Maja Rappard and Tom Watlkins contributed to this report
– The State Department today issued a travel warning for South Sudan, recommending that all Americans "depart immediately," as violence rises in the wake of an attempted coup. That includes non-emergency US personnel, who have already been ordered to depart, forcing the US to suspend normal operations at its embassy there until further notice. At least 66 soldiers have been killed so far in clashes in Juba, the capital of the world's newest country, al-Jazeera reports. Gunshots rang out within earshot of the embassy, and military vehicles roamed the mostly empty streets as residents barricaded themselves inside. The UN says that roughly 10,000 people have sought refuge at the two UN compounds there, according to CNN, and hospitals are straining to deal with an influx of patients.