PESHAWAR: A suicide car bomber Monday killed 10 people at a paramilitary checkpoint in northwest Pakistan, where heavy fighting has sent more than 350,000 people fleeing in little more than a week.

The bomb blast struck the outskirts of Darra Adam Khel, south of the city Peshawar, in a worrying sign that Islamist violence could be escalating away from military offensives designed to crush the Taliban further north.

"Ten people were killed. Three of them died of their injuries in hospital. And seven people are injured," an intelligence official told AFP.

Officials said a six-year-old girl and two security personnel were among those killed when the suicide bomber exploded his car near the checkpost.

No one claimed responsibility for the blast, but Islamists claim or are blamed for the deadliest bombings against security forces, who have been locked for years in fighting against encroaching Taliban militants.

Ground and air forces are waging fresh battles against fighters in three northwest districts in what Islamabad has hailed a fight to eliminate militants -- branded by Washington the greatest terror threat to the West.

Artillery pounded Taliban hideouts in the Swat valley, where around 4,000 militants are estimated to be fighting for control of the former ski resort once popular with Westerners but now devastated by violence.

Interior Minister Rehman Malik said more than 700 militants had been killed in the northwest, but official militant death tolls are unverifiable. Authorities have not released any information on civilian casualties.

It is difficult for reliable, independent information on developments in Swat and neighbouring Lower Dir and Buner to filter across the frontlines, as many local journalists have reportedly fled the violence.

Aid workers said Monday they were stepping up assistance to displaced civilians. A spokeswoman for the UN refugee agency UNHCR said 360,000 had escaped the three worst-affected areas since May 2.

Spokeswoman Ariane Rummery said the provincial government in North West Frontier Province, with the help of UNHCR, had set up 29 registration points for the displaced, mostly in the towns of Mardan and Swabi.

She told AFP: "360,600 individuals registered in camps and outside camps as part of a new influx from Swat, Buner and Lower Dir." "International Medical Corps is expanding critical assistance to the growing number of displaced in the wake of a renewed offensive in Pakistan''s Swat," the US-based organisation said in a statement.

A local Pakistani emergency response official said half a million had fled "since the offensives" but was not able to provide a clear date.

Pakistani security forces have conducted operations against militants in parts of NWFP over the past two years, on top of six years of battles in the surrounding semi-autonomous tribal belt on the border with Afghanistan.

"The number of internally displaced people are more than 500,000 while those registered in camps are 278,000 at Peshawar, Mardan and Swabi," Abid Majeed, an official at the emergency response unit at Peshawar, told AFP.

Most of the displaced live with relatives or rent homes in safer parts of the province, further south away from the fighting, rather than stay in the government-run camps where people sleep under canvas.

Government artillery targeted militant hideouts on Monday in Swat, where an indefinite curfew is now in force, said a military official.

He charged that small bands of militants had moved into houses abandoned by fleeing civilians, where they were hunkered down and firing on the military.

The New York Times warned that terror network Al-Qaeda was seizing on the turmoil to strengthen its presence in nuclear-armed Pakistan and bolster militant Islamist groups.

The daily quoted unnamed intelligence officials as saying that Taliban advances in Swat and Buner, closer to Islamabad than the lawless tribal belt on the Afghan border, have already helped Al-Qaeda in its recruiting efforts.