The death toll in the U.S. drone strikes launched on Saturday morning in Pakistan's northwest tribal area of North Waziristan has risen to 15 with more deaths feared as some of the people injured in the attacks were said to be in critical conditions, according to local sources and media reports.

The drone attacks took place at about 9.30 a.m. (local time) when a suspected U.S. drone fired two missiles in Anzar area of Tehsil Mir Ali in North Waziristan, said the local English TV channel, adding that the drone targeted a house near Mir Ali, a main town in North Waziristan, a stronghold of Taliban militants near the Afghan border.

Security officials claimed that the house was in the use of suspected militants. But local sources said that the identities of those killed were yet to be confirmed.

Tribesmen said they saw three drones flying over the area before the attack and the aircraft were hovering over the area after the attack.

"Rescue efforts were being hampered as drone is still taking flights in the area," a local journalist said, adding that people could not move to the attack site fearing another strike by the U. S. drones.

The United States has increased drone strikes in Waziristan region after a Jordanian suicide bomber killed at least seven CIA agents at a U.S. base in Afghanistan's Khost province in December 2009.

The latest drone attack is also the 216th of its kind since 2008, in which over 900 people, mostly civilians, in the northwest tribal areas of Pakistan, were reportedly killed.

The international community has strongly criticized the U.S. unmanned "licensed-to-kill" drone strikes in Pakistan, which have reportedly killed people by an approximate ratio of 25 civilians to one militant.

Pakistan also publicly opposes the U.S. drone strikes, but the U.S. says that it is an effective operation to eliminate Al-Qaeda and Taliban leaders.

Pakistan Taliban chief Baitullah Mehsood, wanted by the U.S. and Pakistan, was killed in a U.S. drone strike in August last year in South Waziristan. Al-Qaeda's No.3 Mustafa Abul al-Yazid was also killed in a similar strike in North Waziristan last month.