Pakistan has made a formal diplomatic protest to the US over an air strike which killed at least 18 people yesterday.
It is the second protest lodged by Pakistan with its key 'war on terror' ally the US for alleged incursion into its tribal region bordering Afghanistan this month.
Reports say the air attack targeted al-Qaeda's deputy leader Ayman al-Zawahri, on the orders of US intelligence officials.
Pakistani officials said earlier it was unlikely that al-Zawahiri was in Damadola village in the restive Bajur tribal region at the time of the alleged missile attack on Friday morning.
'According to preliminary investigations there was foreign presence in the area and that in all probability was targeted from across the border in Afghanistan,' the Pakistani foreign ministry said in a statement.
'As a result of this act there has been loss of innocent civilian lives which we condemn. The investigations are still continuing,' it added.
Separately, Pakistani Information Minister Sheikh Rashid condemned the incident, without directly pointing the finger at the US.
The air strike provoked retaliation from Pakistani tribesmen, who torched the office of a US-funded aid group.
An estimated 5,000 people gathered at a stadium near Khar, the main town in the Bajur tribal zone, close to the village of Damadola where the air strike occurred.
