OSLO: Donor nations pledged a preliminary $4.8 billion in assistance to Sudan on Wednesday to bolster a fragile 2005 north-south peace in Africa's biggest country that is still torn by violence in its western Darfur province.

Sudan had said it needed $6.1 billion up to 2011, on top of $2 billion in humanitarian aid. A deadly aerial bombing in Darfur three days ago cast a shadow over the Oslo conference and some delegates said it made countries reluctant to pledge openly before a satisfactory explanation.

"This conference is a big success," Luka Biong Deng, minister for presidential affairs for semi-autonomous south Sudan told reporters.

"The international community confirmed it is firm on bringing peace to Sudan, sustaining the peace and giving a peace dividend to its people."

The funds will be split between humanitarian efforts and longer-term development aid favoured by Sudan as it seeks to keep its people behind the 2005 comprehensive peace agreement (CPA), which ended the longest civil war in Africa.

"The implementation of the CPA is more critical than ever. The CPA will benefit not only the Sudanese, it will have ripple effects throughout the region," said senior World Bank official Hartwig Schafer after announcing the pledged total.

Diplomats at the conference condemned Sunday's government bombing attack on a school and marketplace in Darfur, which killed 12 including six children.

International experts estimate 200,000 have died and 2.5 million have been driven from their homes in five years of revolt in Darfur.

Sudan puts the death toll at about 10,000. "The international community cannot make peace in Sudan," said Aid Minister Erik Solheim of host nation Norway which pledged $500 million.

"Peace must be home-grown, and then we can give support in many ways."