Observers from the African Union say the Sudanese air force has bombed villagers in southern Darfur.

Aid agency workers say there are an unknown number of casualties.

The bombing is described as a major ceasefire violation.

Darfur rebels have long said the government has been using its air force against civilians, but Khartoum has always denied doing so.

Meanwhile, the United States is now lobbying the UN Security Council to set up a new court for war crimes suspects in the Darfur region.

The International Criminal Court in The Hague began operating a year ago as the first permanent global criminal court to try individuals for genocide and human rights abuses. But the U.S. opted out because of concerns about frivolous lawsuits being mounted against U.S. soldiers abroad.

Europeans are refusing to subsidize another court with the same purpose.

Renewed fighting in Darfur has resulted in more than 100 dead in the past week, as well as the displacement of a further 9,000 people.

The UN reports that tens of thousands of people have been killed and at least 1.8 million forced from their homes in Darfur since early 2003 when rebels took up arms against the Sudanese government.