The military has released a video showing the bombing of what it calls Taliban targets.

'Overwhelming' refugee crisis

At least 834,000 civilians from the Swat and Buner districts are registered as displaced persons with the United Nations after leaving their homes to escape the fighting.

Antonio Guterres, the UN High Commissioner for Refugees, told Al Jazeera that the scale of the refugee crisis is overwhelming.

"Pakistan has no capacity to deal with these people and to provide them with the basic needs they require. The Pakistani people are in need of massive humanitarian support from the international community," he said from the Swabi refugee camp on Thursday.

"If you look at the movement [of people from the war zone], it is indeed the biggest movement in present times. Massive humanitarian support is required or else there will be a humanitarian disaster."

Buner 'emptied'

The International Committee of the Red Cross (ICRC) said on Wednesday that it had entered Buner, one of the NWFP districts most affected by the conflict.

In depth

 Video: Pakistan's sovereign fight
 The fight for northwest Pakistan
 Riz Khan: Obama's 'AfPak' strategy
 Riz Khan: The battle for the soul of Pakistan
 Q&A: The struggle for Swat
Talking to the Taliban
Pakistan's war
 Pakistan diary
 Your views: Crisis in Swat

"You can see the scars of recent fighting," Bart Janssens, the ICRC's health co-ordinator in Pakistan, said.

"There is no more electricity or clean drinking water. Most shops are closed. Goods on the market are scarce. The streets feel empty. The district is rapidly being emptied of its inhabitants."

The Pakistani military has up to 15,000 troops in place against about 4,000 Taliban fighters in the northwest of the country.

At least 750 suspected Taliban fighters and 33 troops have died in military operations in Lower Dir, Buner and Swat since April 26th, the military says.

The military onslaught comes after increasing pressure by the US government to take a stronger line against the Taliban.

The Taliban on Wednesday issued an ultimatum to provincial leaders in Pakistan, with a spokesman for the group telling Al Jazeera that the officials must resign or else their families would be targeted.

Drone co-operation

In another development, reports in the US media say that the Pentagon has shared with Islamabad surveillance data gathered from drones flying over Pakistani territory.

But "it is not clear" whether that co-operation will continue, the New York Times reported.

Pakistan has in recent months stated its opposition to US drone overflights. Bombs launched from drones have been responsible for the deaths of at least 390 people in Pakistan, many of them civilians, since August 2008.

Islamabad has called the drone overflights and bombing runs a violation of its territorial sovereignty.

Asif Ali Zardari, the Pakistani president, said on Wednesday that he had asked Washington for "ownership" of US drones carrying out attacks on its territory.

Islamabad was "negotiating terms" with Washington over the use of the drones, he said, after talks with Gordon Brown, the British prime minister, in London.