A mortar shell hit a house in a valley where Pakistani security forces are battling Islamic militants, killing a family of seven, and militants torched a nearby girls school, police said Thursday.

Government officials struck a peace deal with militants in the northern Swat valley in May, hoping to curb the growing influence of militant groups through negotiations.

But U.S. and NATO officials complain that cease-fires and talks across Pakistan's wild border zone have allowed Taliban and Al Qaeda insurgents based there to focus on attacks in neighboring Afghanistan.

Trouble flared in Swat on Tuesday when militants abducted 25 members of the security forces. Since then, fighting has reportedly killed 27 rebels and seven troops and raised doubts about the new government's ability to combat militancy.

The provincial government described the situation in the Swat valley as "grave" and said it had requested more army troops to help bring peace, law and order.

The shell hit overnight in the village of Deolai, said Shakoor Khan, a police official in the nearby town of Kabbal. A man called Mohammed Tahir died along with his wife and five children, Khan told The Associated Press by telephone.

It was unclear who fired the mortar round.

Khan also said that militants burned a girls school in the Khwazkhela area, the latest in a string of similar attacks blamed on Islamic fundamentalists opposed to female education.

The army reported sporadic overnight gunfire in the valley. It didn't confirm Pakistani media reports of renewed fighting Thursday. A valley-wide curfew was relaxed for two hours before noon to allow residents to buy provisions.

The valley lies just 90 miles from the capital, Islamabad and is a vital test of the government's resolve to prevent Taliban-style militancy from spreading into previously peaceful areas of the northwest.

Officials and militants in Swat blame each other for violating the peace accord, though neither side has declared the agreement dead.

While Western governments back the 4-month-old government's efforts to win over more moderate armed groups, they want Pakistan to take tougher action against hard-liners.

Followers of Mullah Fazlullah, a militant cleric who rallies support using a pirate FM radio station, seized parts of Swat last year before an army offensive drove them into the mountains.

Also Thursday, the military announced that it was abandoning a fort in the militant stronghold of South Waziristan that has repeatedly come under attack.

Maj. Gen. Alam Khattak, who commands paramilitary troops operating along the frontier, said security forces were leaving Ladha Fort at the request of tribal elders.

Khattak said the fort, which will be turned into a 20-bed hospital, was too close to residential areas and that the military was negotiating for a site to build a new fort.

He didn't say if the pullback was a condition for a peace deal with local tribes, which include top Taliban leader Baitullah Medsud, but added: "the fighting phase is over in his area, and now negotiations are being held with the people."