Tensions in the border region are rising
At least five people have been killed in another suspected US missile strike on militant targets in Pakistan's border region, Pakistani officials say.
Officials said a missile was launched by a suspected US aircraft in the North Waziristan tribal area.
Pakistan's army says it is investigating the incident.
It would be the third attack in three days allegedly carried out by US forces, who have not officially confirmed their involvement.
Some reports say Islamist militants were killed in Friday's attack, while local TV channels said women and children were among the dead.
Witnesses said missiles fired by an unmanned aircraft hit one or two houses in the village of Kurvek, about 30km (18 miles) west of the main town of Miranshah in North Waziristan.
"Two drones were flying in the area. They fired three missiles," one unnamed witness told Reuters news agency.
Several people are reported to have been injured in addition to those killed.
Pakistan's military spokesman Maj Gen Athar Abbas said reports of the incident were being investigated.
"Pakistani forces did not carry out any activity in the area," he told the AFP news agency.
The BBC's Barbara Plett in Islamabad says this would be the third such attack in three days, including an unprecedented ground assault allegedly carried out by American commandos.
In recent months US forces have stepped up unilateral strikes on Taleban and al-Qaeda targets in Pakistan's tribal areas.
They say Pakistan - a key US ally in the "war on terror" since 2001 - is not doing enough to stem the flow of insurgents across the border into Afghanistan.
Pakistani security officials suspect the Americans are trying to hit senior al-Qaeda targets ahead of forthcoming US presidential elections, our correspondent says.
At least two senior al-Qaeda figures are believed to have been killed in US missile strikes on Pakistani territory this year.
A senior al-Qaeda leader in Afghanistan, Abu Laith al-Libi, was reported killed in February, while Midhat Mursi al-Sayid Umar, described as a leading al-Qaeda chemical weapons expert, died in July, reports said.
It is not clear who the targets of strikes this week might have been.
On Thursday, at least five people were killed in a missile strike in the village of Mohammad Khel near Miranshah. Officials said all five were low-level militants of Arab origin.
Meanwhile, large numbers of people have decided to leave their settlements near Angor Adda in South Waziristan.
The town was attacked on Thursday by foreign troops carried across the border from Afghanistan by helicopter, Pakistan's government says.
Officially, the US military has no knowledge of such an incursion, but Pentagon sources have confirmed that US commandoes carried out the raid.
Pakistan responded furiously, summoning the US ambassador and calling the attack a gross violation of its sovereignty.
Pakistan's army has warned that such direct US action could rally more tribesmen behind the Taleban and incite a wider uprising.