President Omar al-Bashir of Sudan paraded his defiance of an international arrest warrant for war crimes before thousands of supporters today as police visited the offices of international aid agencies to seize computers following a government expulsion order.

The cheers of the dancing crowds stood in sharp contrast to the sudden gloom in Darfur where two million people dependent on aid stared into the face of a humanitarian catastrophe as aid workers departed.

Fears are growing, too, that the expulsions are a prelude to a new military offensive unseen by Western eyes.

Khartoum ordered ten leading aid agencies to leave the country today in retaliation for the International Criminal Court’s decision to issue an arrest warrant for Bashir, accusing them of passing information to the court.

The ten agencies account 70 per cent of the humanitarian aid delivered to displaced people in camps in Darfur in the form of food, shelter, clean water and medicine. Mercy Corps called the decision a “devastating blow” for the people of Darfur while Save the Children UK warned that the lives of thousands of children were now at risk.

Oxfam GB said it had joined forces with other agencies to appeal the government’s decision. United Nations officials began emergency negotiations to strike a deal allowing the agencies to continue their operations.

“We’ll do whatever we can to stay,” Ian Bray, an Oxfam spokesperson, said.

David Miliband, the Foreign Secretary, added his voice for those calling for Khartoum to back down. “We are very concerned by any threat to stability or the even greater threat to human existence inside Sudan,” he said in Brussels.

The aid agencies “are innocent parties in this dispute, they are working solely to protect the lives and livelihoods of innocent individuals.”

But today the Government revoked the visas of all foreign personnel and began seizing assets they had demanded be handed over from vehicles to laptops.

Aid workers were scrambling to salvage crucial data on their Darfur operations before computers were seized for investigation by the Sudanese authorities.

Hassabo Mohamed Abd el-Rahman, head of the government’s Humanitarian Aid Commission, said some groups had “passed evidence to the ICC” and made false reports of genocide and rape. All the agencies have denied any cooperation with the ICC.

Mr Al-Bashir, who faces charges of war crimes and crimes against humanity, is accused of orchestrating a scorched earth anti-insurgency campaign in Darfur in which civilians were massacred, raped and driven from their homes.

Speaking publicly for the first time since the warrant was issued, Mr al-Bashir told a meeting of his Cabinet that the court, the UN and the aid organisations were colluding to take control of the country and steal its vast oil reserves.

“We are ready to resist colonialism,” Mr al-Bashir told crowds of roaring supporters at a rally in Khartoum, dancing and jabbing his cane in the air as he spoke. “We are ready to defend our religion.”

Mr al-Bashir’s calls were heeded by his neighbours in the African Union, who announced yesterday that they would send a high-level delegation to New York to lobby the UN Security Council to defer the warrant.

The AU and the Arab League have denounced the court’s decision, warned that it will destroy any hopes of finding peace in Darfur and may also wreck the already troubled peace process between Khartoum and the semi-autonomous South.

China, Sudan’s most important investor, urged the Security Council to suspend the warrant.

In Darfur, the joy at the court's decision was quickly replaced by fear and uncertainty. “Inside people are happy,” said a resident of Abu Shouk displacement camp in north Darfur, who asked not to be named. “But everyone is keeping quiet. Nobody goes outside."

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