SHAGUNA NAKA: Pakistan's military suspended a curfew Friday in a northwest city where it is fighting Taliban guerrillas, officials said, allowing tens of thousands of civilians to flee the area.

In what is emerging as a grave humanitarian crisis, hundreds of thousands of desperate civilians have been trying to get to safety from the Swat valley, where the army launched a new offensive late last month to crush the militants.

The government suspended a curfew for people going out of Swat's main city of Mingora from dawn until mid-afternoon, and local administration chief Arshad Khan said residents had been advised to leave -- and were doing so.

"People are leaving in large numbers," Khan said. "They are vacating their homes."

Hundreds of vehicles including buses, cars, rickshaws, pickups and motorbikes were seen crossing the Shaguna Naka checkpoint at the exit of the conflict zone.

People sat on the roofs of buses and backs of trucks with their bedding and clothes as they headed for Mardan 30 kilometres (18 miles) away where authorities have set up camps for the displaced people.

"The situation is very, very bad. We have no hope for life," said a young man who identified himself only as Ibrahim.

He said he came with 30 people who fled Odigram village near Mingora to escape the fighting.

"We are going to Mardan. We are just going to sit under a tree somewhere. We just want some safety for our children," he said.

"It was painful, every second we thought we were dying. There was a lot of bombing and shelling," he said, adding that the entire market in his village was destroyed.

The military says its forces have encircled Mingora, which is held by Islamist fighters who have waged a brutal insurgency to extend their control and enforce an uncompromising version of Muslim sharia law.

The advance of the militants closer to the capital Islamabad has raised concern in the United States, which has put Pakistan at the centre of its efforts to contain another Islamist insurgency in neighbouring Afghanistan.

But there are also concerns that the army campaign -- including artillery bombardment, attacks by helicopter gunships and commandos dropped behind Taliban lines -- will grow more and more unpopular among Pakistani civilians.

Naeem Akhtar from Mingora who works in a bank was travelling with his wife and two children in his car riddled with bullets.

He said he was furious over the military action, and accused the army of destroying his house.

"Four members of my family were killed in shelling. The army did it. We have spent last two weeks just like in hell. It's not due to Taliban, it is due to the armed forces. We just want out of Swat and we would find some safe place."

An official from the International Committee of the Red Cross, which this week was able to enter one of the hardest hit districts, said there was no longer any electricity or fresh drinking water.

The military says up to 15,000 troops are taking on about 4,000 well-armed fighters in Swat, where Islamabad has ordered a battle to "eliminate" the militants branded by Washington as the greatest terror threat to the West.

The fighting has sent more than 800,000 people fleeing Swat as well as the areas of Lower Dir and Buner, while hundreds of thousands are believed still trapped in the conflict zone.

Pakistan's military insists it is taking all possible measures to lessen civilian casualties and avoid populated areas, but analysts have warned that general public support for the offensive could sour as the human cost soars.

Before Friday, the military estimated that around 200,000 people remained in Mingora.

Based on combined military tolls, more than 870 militants and 42 troops have been killed in operations in Swat as well as Lower Dir and Buner, though there is no independent confirmation of the figures and no word on civilian deaths.

The Swat valley was once a picturesque ski resort popular with Westerners, but now it is the crucible of a fierce battle between emboldened Islamist militants and a government under intense pressure to rein them in.