UN Secretary General Ban Ki-moon called Wednesday on Sudan to conduct a full investigation into an attack that killed four peacekeepers in Darfur, his spokesman said.

Martin Nesirky said Ban was "appalled and deeply saddened" by the ambush Tuesday of a patrol by UN-African Union peacekeepers in El Geneina, West Darfur.

Four Nigerian peacekeepers were killed and eight others were wounded.

"The secretary general urges the government of the Sudan to conduct a full investigation and to ensure that the perpetrators are swiftly brought to justice," Nesirky said.

Ban "expresses his condolences to the government of Nigeria and to the families of the fallen peacekeepers and UNAMID," he said.

The peacekeeping force, which numbers 23,500, has been deployed in Darfur since 2007 in an attempt to end hostilities between rebels and the Sudanese government.

Later Wednesday, the 15-member Security Council also condemned the ambush.

It called on the government of Sudan to "swiftly investigate the incident and bring the perpetrators to justice."

The council reiterated its support for the UN peacekeeping mission in Darfur and called on all parties there to cooperate with it.