PESHAWAR (REUTERS) - A suspected US drone aircraft killed at least seven militants in Pakistan's ethnic Pashtun tribal region on the Afghan border on Friday, Pakistani security officials and residents said.

US drones have fired missiles into troubled and inaccessible border areas such as North Waziristan, the main stronghold for militant groups aligned with Al-Qaeda and the Taleban, since 2004.

Pakistan has been angered by reports of civilian casualties and what it sees as a violation of its sovereignty, and the United States has reduced their use in recent years.

In the early hours of Friday, drones fired two missiles on a compound in the village of Dargah Mandi in North Waziristan, destroying the house and killing seven people.

Security officials said all those who were killed were insurgents. The area where the attack took place is known as a stronghold for the Haqqani network, which regularly attacks US forces in Afghanistan from its mountain hideouts in Pakistan.

US drone strikes in Pakistan have fallen significantly over the past two and a half years, totalling 20 this year.

There were 48 in all of 2012 and 73 in 2011, according to a tally kept by the New America Foundation.

It is hard to check their impact on both militants and civilians because independent observers and journalists have almost no access to the areas where most of the strikes occur.