At least 16 people, including two women and a child, have been killed and around a dozen injured as a US drone attacked a house in Pakistan's tribal area along the Afghan border.
A security official said a pilotless US drone Friday fired two missiles at a house in Mohmmad Khel village in North Waziristan.
The compound that was demolished in the strike, belonged to an Afghan refugee, who is believed to regularly host insurgents launching cross-border attacks on US-led international forces in Afghanistan.
More casualties were feared as some people were buried under the rubble, said the official, who spoke on condition of anonymity.
Aaj news channel reported that 21 people were killed in two separate strikes by a suspected US guided missile and jets in the tribal district.
Most of the killed and injured were foreigners, the report said.
A spokesman from the Pakistan Army initially denied the reports, saying the US planes only hit targets on Afghan side of the border.
"The International Security Assistance Force had informed us beforehand about their operation along the border in Afghanistan," Major General Athar Abbas said.
Later, his deputy Major Murad Khan told DPA that "an explosion was heard in the area, but the cause of incident was not known and it was being ascertained."
The US attack came three days after two missiles fired from a US drone killed six people in North Waziristan, which is regarded as a haven for Taliban militants and members of the Al Qaeda terrorist network.
Having complained about Islamabad's inability to eliminate the hideouts of the Taliban, US forces have stepped up strikes inside Pakistan, causing tension between the two countries.
Pakistani and US forces have officially admitted an exchange of fire at least once in recent weeks.
Islamabad says it has deployed around 120,000 troops along the Afghan border to try and quell the Taliban insurgency in various areas, including Bajaur Agency, where between 500 and 1,000 Taliban fighters have been killed in the offensive that started in August.
On Friday, fortified militant positions and hideouts were targeted around Loi Sam area with helicopter gunships and artillery fire, Major Murad, said.
"Seven miscreants were killed and numerous were injured," Khan said.
The militants have responded to the operation with more suicide and other attacks across the country.
A suicide truck bombing hit Islamabad's Marriott hotel last month, leaving at least 53 people, including the Czech ambassador, two US marines and a Danish intelligence officer.
More than 250 people were injured in the attack, which caused panic among Westerners in the country.
The British embassy and UN mission raised security levels for their foreign staff and ordered the evacuation of their children this week.
A Poland-based oil firm, Geofizyka Krakow Limited, working in central Punjab, repatriated its 11 employees after a Polish electrician was kidnapped and his two guards killed on Sep 27.
An official from the firm told DPA Friday on condition of anonymity that nine remaining Polish employees would also leave the country soon.
The Pakistani authorities have confirmed that Peter Stanczak was in Taliban custody, a spokesman for the Polish Ministry of Foreign Affairs said.
The ministry "got an assurance that Pakistani forces are leading an intensive effort to free our citizen," a statement from spokesman Piotr Paszkowski said.