UN: The Sudanese government is limiting the ability of international aid organisations to reach millions of people in Darfur, according to a United Nations senior humanitarian official.
Jan Egeland, the UN's emergency relief co-ordinator, rounded off a three-day trip to Sudan by criticising Khartoum's red tape, which is hindering attempts to ease conditions in the state's troubled western region.
Movement of foreign journalists has also been restricted in the past fortnight, just as reports began to emerge of a major government offensive against rebel positions in north Darfur.
Government Antonov bombers and their Janjaweed allies launched assaults on rebel strongholds around the town of Birmaza on Thursday. Rebels said as many as 70 people had died in ongoing fighting and African Union monitors confirmed there had been a "heavy toll on the civilian population".
"We have split into two or three groups and all have fighting," Jar el-Neby, a commander from the rebel National Redemption Front, told Reuters.
"The government did not use planes yesterday but today the Antonovs are circling."
The Sudanese government has repeatedly played down the extent of the conflict in Darfur.
While international agencies estimate that 200,000 people have died and more than two million people have been displaced during 3½ years of fighting, Sudanese president Omar al-Bashir recently said as few as 10,000 people had been killed.
Meanwhile, the regime is becoming increasingly suspicious of western aid agencies and journalists. Mr Egeland's own trip to Darfur was cut short by the government's national security apparatus, which ruled out visits to four of the six locations on his itinerary.
Two US journalists were also banned from flying with the UN mission - part of a response to movement restrictions on Sudanese diplomats in Washington.
Two weeks ago the government stopped issuing travel permits to journalists, preventing independent access to Darfur.
Mr Egeland, who steps down from his position at the end of the year, said he was frustrated at Khartoum's unwillingness to assist what has become the world's biggest aid effort, delivering support to some four million people.
"There are NGOs here who have half of their staff sitting in Khartoum because they have no travel permits," he said.
"They do not get visas, they have to spend more of their time doing paperwork than helping people. It cannot go on like that. The Sudanese should help us help their people, not prevent us from helping them."
International NGOs face a growing burden of bureaucracy. Workers must pay $120 (€94) for an exit visa simply to leave the country. Applications can regularly take more than six weeks to process. Delays in issuing exit visas and work permits frequently mean foreign staff end up as illegal aliens, unable to work or travel out of Khartoum.
One charity, the Norwegian Refugee Council, pulled out of Darfur earlier this month following its temporary expulsion from Kalma Camp in South Darfur - the fifth time it had been ordered to suspend its operations there. It has since been ordered to hand over all its cars, radios and other assets to the government.
Other charities which have spoken publicly about the crisis have found themselves under investigation for supposed criminal activity or smeared in state-controlled media.
Two senior members of Médecins Sans Frontières Holland were charged with espionage and publishing false information after the organisation issued a report on hundreds of rape victims they had treated in Darfur.
A senior aid official, speaking on condition of anonymity, said the government was determined to drive NGOs from the country.
The charges are denied by Kosti Manibe, minister of humanitarian affairs.