South Sudan's army said on Sunday it had completed its pullout from an oil field seized from Sudan, ending a deadly standoff which forced thousands of civilians to flee. South Sudanese officials said the withdrawal from Heglig had been ordered to avert a return to all-out war, but they accused Khartoum of air strikes against the departing troops. The South seized Sudan's most important oil field Heglig on April 10, claiming Khartoum was using it as a base to attack the South's oil-producing Unity State. A senior Sudanese official, Nafie Ali Nafie, said on Sunday that 400 Southern troops "and mercenaries" were killed during the days-long standoff. Such figures are impossible to verify. Heglig is internationally regarded as part of Sudan, although South Sudan disputes it. The 10-day occupation by the world's newest nation met widespread criticism, including from UN chief Ban Ki-moon, who called it illegal. Foreign powers have also called for an end to Sudan's cross-border air raids. South Sudan's President Salva Kiir on Friday announced his forces would carry out "an orderly withdrawal" from Heglig. The SPLA "completed its withdrawal from Heglig yesterday," Sudan People's Liberation Army (SPLA) spokesman Philip Aguer told AFP on Sunday.But he charged that Khartoum's air force "continued bombing on the night of the (Friday April) 20th and in the morning of the 21st". On Friday Sudan said its soldiers had "liberated" the oil field by force, despite Kiir's earlier announcement of a pullout. The South Sudanese UN ambassador Agnes Oswaha said Juba decided to withdraw "because it does not wish to see a return to war." The Heglig violence was the worst since South Sudan won independence in July after a 1983-2005 civil war in which about two million people died. Heglig's entire population fled the standoff, leaving thousands of civilians displaced in the open, the United Nations said on Sunday. "According to the government of Sudan's Humanitarian Aid Commission (HAC) and other reports received by the UN, the entire civilian population of Heglig town and neighbouring villages fled," the UN's humanitarian agency said. The report cited HAC figures saying 5,000 people had escaped from Heglig. South Sudan's withdrawal followed intense international diplomacy to pull the two sides back from the brink of a wider war. US President Barack Obama on Friday called for them to "have the courage to return to the table and negotiate and resolve these issues peacefully." Kiir heads to China on Monday for an official visit to a country long-considered Khartoum's ally, although Beijing has developed closer ties with Juba, notably in the petroleum sector. "China's position on that issue is to promote dialogue and urge peace. It does not favour any side," said Li Guangyi, professor at the Institute of African Studies at the University of Xiangtan in central China. Li added that fighting benefits neither Sudan, South Sudan, nor China. The African Union (AU), which has for years sought to broker a sustainable peace between the rivals, on Sunday again called for "a complete cessation of all hostilities," and a swift resumption of talks. Both sides should consider their "responsibility towards their region, the rest of Africa and the larger international community," the AU statement said. Each country has accused the other of damaging the oil infrastructure at Heglig, which accounted for about half of the north's production. Also on Sunday, Sudanese rebels claimed to control part of the strategic town of Talodi, denying they had suffered heavy losses during fighting there. "Fighting is continuing inside the town," about 130 kilometres (80 miles) northeast of Heglig, said Arnu Ngutulu Lodi, spokesman for the Sudan People's Liberation Movement-North (SPLM-N). The rebels deny Khartoum's allegations that they are supported by the South. Amid a mood of nationalist fervour after Sudan "liberated" Heglig, a Muslim mob destroyed a church compound in Khartoum, a church official said. Pastor Yousif Matar Kodi said hundreds of people descended on a farm and training compound run by the Sudan Presbyterian Evangelical Church on Saturday morning, torching buildings.