Tension in Pakistan's north-west has increased in recent days
Pakistani officials say 12 militants have died in a missile strike in the tribal area of South Waziristan, close to the border with Afghanistan.
Four missiles were fired on Tuesday night at a compound near the border. The US military in Kabul has denied it was behind the missile strike.
Such bombings are a regular tactic used by American forces targeting Taleban and al-Qaeda fighters in Pakistan.
Separately, heavy fighting is going on in other parts of north-west Pakistan.
In the Kurram area, inter-tribal fighting has claimed more than 100 lives since the end of last week, officials say.
In the Bajaur tribal region, the Pakistani army says more than 150 militants and 13 soldiers have been killed in a week of fighting. Militants put their dead much lower, at about a dozen.
Officials said four missiles hit a compound, occupied by local Taleban, in the troubled Baghar region of South Waziristan late on Tuesday.
Locals told the BBC Urdu service that six of the dead were Pakistani militants, and six were foreigners. There is no word yet on their identities.
An al-Qaeda weapons expert is believed to have been killed in a similar strike last month.
It remains unclear who fired the missiles, or where they were fired from.
The BBC's Mark Dummett in Islamabad says such strikes, which are often launched by pilotless-drones, are extremely unpopular in Pakistan.
The government in Islamabad complains that the Americans do not tell them when they are going to launch attacks.
On this occasion, witnesses said Pakistani helicopters had been seen hovering over the area soon after the strikes.
Security has deteriorated sharply in recent weeks along the Pakistani border with Afghanistan.
There is mounting US pressure on the Pakistani government to crack down on militants, who use the border region to launch cross-border raids into Afghanistan.
The Afghan government and Nato say that the border region is a haven for al-Qaeda and Taleban militants. Pakistan denies it could do more to curb militancy.
In Bajaur region, more than 30 civilians have died in fighting between troops and militants over the past week, reports say.
Kurram has been paralysed by sectarian strife
Fierce clashes between the troops and the Taleban broke out more than a week ago when troops tried to set up a post at a strategic location in Loi Sam, on the Afghan border.
The troops had to retreat to Bajaur's administrative and military headquarters, Khar, after the local Taleban intensified their attacks.
During the past couple of days, the militants established several positions between Loi Sam and Khar, and laid siege to Khar itself, provoking heavy attacks from the government forces.
Militant spokesman Maulvi Omar told the BBC Urdu service: "Since we have succeeded in stopping the advance of the government troops, the occupation of those positions is not required."
More than 100 people have also been killed over the past week in fighting between the Turi and Mangal tribes in Kurram, a tribal district on the border with Afghanistan, officials say.
The BBC's M Ilyas Khan in Karachi says that sectarian fighting has paralysed life in Kurram since November 2007 and hundreds of people have been killed.
Shias are the majority in the region, but they are surrounded by Sunni tribesmen.
Both sides are reportedly using heavy weapons. Independent verification of the casualty figures is difficult due to the absence of communication links in the area.
The only road into the region has remained cut off since November, causing food and medicine shortages.