Pakistani troops are deployed against militants in tribal areas
A suspected pilotless American drone has fired missiles in a border area of Pakistan, killing at least six people, Pakistani intelligence officials say.
Officials said a house was hit near the town of Mir Ali in North Waziristan and nine people were also injured.
Some reports say the missiles were fired after the drone was shot at.
A spokesman for US forces in Afghanistan told the BBC News website that he "was not aware" of a drone attack taking place.
The Pakistani army has not commented on the incident.
Tension between the US and Pakistan has increased over cross-border incursions against militants by American forces based in Afghanistan.
North Waziristan is known as a haven 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, according to some reports, the house of a local Taleban leader was struck near Mir Ali, but the reports are not confirmed.
She says there is no clear indication as to who was killed in the missile strike.
The United States has stepped up missile attacks from drones in the region in recent weeks.
It says that they are used against militant targets, but our correspondent says that sometimes intelligence failures have led to civilian casualties.
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, our correspondent says.
3 Sept: First reported ground assault by US troops in Pakistan - Islamabad responds furiously
15 Sept: Pakistani troops reportedly fire in air to stop US troops crossing in S Waziristan
17 Sept: Top US military chief Adm Mike Mullen visits Pakistan to calm tensions
16 Sept: Pakistan says it was not told of fresh US missile strike
22 Sept: Pakistani troops in fresh firing to deter US incursion into N Waziristan, officials say
25 Sept: Pakistani troops fire warning shots at Nato helicopters on border with Khost
Last week, the Pakistani army said it was investigating the wreckage of a suspected US spy plane found in South Waziristan, although it dismissed suggestions the aircraft had been shot down.
Pakistan has protested to Washington about US strikes into its territory, including a raid by commandos on 3 September in which several Pakistanis were killed.
Pakistani and US troops are also reported to have exchanged fire across the border last week.
President Asif Ali Zardari has said he will not tolerate violations of his country's territory.
But in a statement released on Monday, the US State Department affirmed "its support for Pakistan's sovereignty, independence, unity, and territorial integrity".
The statement was released after a meeting in Washington between the US Deputy Secretary of State John Negroponte and Pakistani Foreign Minister Shah Mehmood Qureshi.