UN accuses Sudan of bombing Darfur

Refugees are also coming under attack in southern Darfur from the pro-government Janjaweed militia, it said.

The lobby group Human Rights Watch has also accused Sudan of breaking pledges to rein in the militias. In a report, HRW said that the outside world had failed to prevent atrocities that have forced many people to flee.

The Sudanese ambassador to Britain, Dr Hassan Abdin, rejected Human Rights Watch accusations that Janjaweed militiamen were being incorporated into government security forces in Darfur.

"To talk of governments acting in connivance and collaboration with the Janjaweed is not true," Abdin told the BBC's World Today programme.

He said Sudan was acting to rein in the militia and had arrested and tried 100 of its members.

The UN's office for the co-ordination of humanitarian affairs is highly critical of the Sudanese government. It says that despite promising to improve humanitarian access, Khartoum has been placing so many restrictions on aid workers that access has actually got worse over the past week.

Flights operated by the World Food Programme have been inexplicably grounded, for example, while other aid agencies say they are having difficulty recruiting local staff because of government-imposed restrictions and delays.

The UN refugee agency says that Sudan's government is putting pressure on internally displaced people to return to their villages, despite concerns over safety.

Last week, the Sudanese government and the UN agreed on a plan to tackle the Darfur crisis, which included measures to provide safe areas around certain towns and villages.

"We have interviewed people in hospital who tell us they have gone back to the villages... and have been shot by Janjaweed raiders," says United Nations High Commissioner for Refugees spokesman Peter Kessler in Geneva.