A US drone has fired a missile for the first time in territory controlled by Pakistan's most wanted militant, Baitullah Mehsud, officials say.
Local people say that at least one person was killed in the attack in South Waziristan. Intelligence officials said five people died.
Reports say the drone may have been targeting a group of Uzbek militants.
Meanwhile, police in the district of Swat say a suicide bomber has killed at least two policemen.
There have been a series of US drone attacks inside Pakistani territory along the border with Afghanistan in recent weeks.
The latest reported attack took place in the village of Sam near Ladha in South Waziristan. South Waziristan is the base of Baitullah Mehsud who leads the loose coalition of militants known as the Pakistan Taleban.
The previous government accused him of masterminding the killing of former Prime Minister Benazir Bhutto in December 2007.
Pakistani officials say that about 80% percent of more than 70 suicide bombings across the country since July 2007 have been carried out by members of his Mehsud tribe.
Local residents in South Waziristan said that spy drones were still circling over the area of the missile strike and people feared further attacks.
The US says the drones are used against militant targets, but correspondents say that sometimes intelligence failures have led to civilian casualties.
Alleged missile strikes by the US are controversial in Pakistan
At the beginning of this month Pakistani intelligence officials said that a suspected pilotless American drone fired missiles near the town of Mir Ali in North Waziristan which killed at least six people.
Tension between the US and Pakistan has increased over cross-border incursions against militants by American forces based in Afghanistan.
Both North and South Waziristan are known as havens for Taleban and al-Qaeda fighters who enter Afghanistan.
Foreign fighters from Uzbekistan, Afghanistan and the Middle East are all thought to be based there.
The BBC's Barbara Plett in Islamabad says that such attacks seem likely to continue as long as US and Nato forces in Afghanistan believe that Taleban and al-Qaeda forces are taking refuge in Pakistan's tribal areas.
Police say that Thursday's attack in Swat happened when a suicide bomber drove an explosives-laden vehicle into a police compound, killing at least two policemen.
Part of the police compound was destroyed in the attack
A number of militants opened fire on the compound in Mingora in Swat valley before the bomber attacked, police say.
More than 30 people were injured, some of them seriously.
Correspondents say the security situation in Swat has been steadily deteriorating since the breakdown in the summer of a peace agreement between the government and pro-Taleban cleric Maulana Fazlullah.
The Swat valley, once Pakistan's most famous tourist destination, has been the scene of an insurgency by his followers since 2007.
They want to enforce his version of Islamic Sharia law in the region.
Meanwhile, officials say that militants in the neighbouring district of Dir have taken four guards hostage at a jail in Timergara.
There are several Taleban militants among about 400 prisoners being held in the jail.