ISLAMABAD, May 19, 2009

The human exodus from the war-torn Swat valley in northern Pakistan is turning into the world's most dramatic displacement crisis since the Rwandan genocide of 1994, the UN refugee agency warned.

Almost 1.5 million people have registered for assistance since fighting erupted three weeks ago, the UNHCR said, bringing the total number of war displaced in North West Frontier province to more than 2 million, not including 300,000 the provincial government believes have not registered. "It's been a long time since there has been a displacement this big," the UNHCR's spokesman Ron Redmond said in Geneva, trying to recall the last time so many people had been uprooted so quickly. "It could go back to Rwanda."

The army reported fierce clashes across Swat, a tourist haven turned Taliban stronghold. After a week of intense aerial bombardment with fighter jets and helicopter gunships the army has launched a ground offensive to drive out the militants to rout the militants from the valley. Commandos pushed through the remote Piochar valley, seizing a training centre and killing a dozen Taliban, a military spokesman, Major General Athar Abbas, said. Gun battles erupted in several villages surrounding Mingora, Swat's main town. Abbas said the military had killed 27 militants, including three commanders, and lost three members of the security forces. The figures could not be verified, as Swat has been largely cut off since the operation started.

The Taliban leader in Swat, Maulana Fazlullah, remains at large. His spokesman vowed the rebels would fight until their "last breath".

The operation continues to enjoy broad public support. Opposition parties endorsed the action at a conference called by the government, dispelling the notion that the army was fighting "America's war".

But that fragile unity could be threatened by heavy civilian casualties or a further deterioration in the conditions of the 2 million displaced. Returning from a three-day trip to Pakistan, the UNHCR head António Guterres termed the displacement crisis as "one of the most dramatic of recent times". Relief workers were "struggling to keep up with the size and speed of the displacement," a statement said.

The main difference with African refugee crises such as Rwanda, however, is that a minority of people are being housed in tented camps. According to the UN just 130,000 people are being accommodated in the sprawling, hot camps in Mardan and Swabi districts, while most are squeezed into the homes of friends or relatives, with as many as 85 people in one house.

Nevertheless aid workers and political analysts warn that if international aid to ease the crisis is not urgently delivered, the strain on the displaced and those helping them could lead to political destablisation. Acknowledging the scale of the crisis, the prime minister of Pakistan, Yousaf Raza Gilani, said: "The displaced men, women and children should not feel alone. We won't leave any stone unturned in providing them help and protection."

The UN is expected to launch an international appeal for aid running into hundreds of millions of dollars in the coming days.