Britain is the second-largest donor to Darfur, where almost four years of conflict have forced 2.5 million people to flee their homes and killed an estimated 200,000 in violence Washington calls genocide. "It is of critical importance that the international community provides early and adequate finance to sustain the massive humanitarian response needed in Darfur," Hilary Benn, the minister for international development, said yesterday. Britain has already given a total of 230 million to Darfur. This week the United Nations launched an appeal for about $653 million (332 million) in 2007 to fund emergency aid and development in Africa's largest country, torn apart by multiple civil wars. The Sudanese government has signed three peace deals in less than two years to try to end regional insurgencies. But in Darfur, violence has increased since a deal was signed with only one of three rebel negotiating factions in May. The rebels who rejected the agreement formed a new alliance and renewed hostilities with the government in June. The UN said yesterday that an international aid agency convoy was ambushed near el-Geneina this week. One aid worker was shot in the leg and a policeman was killed. Attacks in Darfur this month have forced 400 aid workers to be evacuated. Sudan rejects a UN Security Council resolution authorising 22,500 UN troops and police to take over from an African Union peacekeeping mission, with Khartoum calling it an attempt at Western colonisation. But critics say it fears those troops would arrest officials for alleged war crimes.