The UN High Commissioner for Refugees, UNHCR, said in a statement on Monday that Idriss Deby, the president of Chad, who accuses Sudan of backing rebels that attacked the capital N'Djamena last week, had promised that nobody would be forced to leave.

Antonio Guterres said: "I ... am pleased to report that he (Deby) has reaffirmed that refugees will not be 'refouled' (forcibly returned) and Chad will abide by international principles."

But Guterres, who spoke to Deby on Sunday night, said the Chad leader had repeated his concerns about the difficulty of providing security for the refugees and the humanitarian organisations that were helping them.

"UNHCR strongly appeals to the international community and its various organisations to do everything possible to urgently establish peace and security in Darfur," the former Portuguese prime minister said in the statement.

Last Thursday's attack on the capital was the boldest yet by rebels who have pledged to end Deby's nearly 16-year rule and block a May 3 presidential poll in which he is standing for re-election.