Pakistani security officials say a suspected U.S. drone attack has killed at least six militants near the country's border with Afghanistan.

The officials say unmanned aircraft fired two missiles Tuesday at a suspected militant compound in Miranshah, the main town in Pakistan's tribal area of North Waziristan.

The area is known as a stronghold of Taliban and al-Qaida-linked militants. Pakistan has been under increasing pressure to do more to dismantle the havens that Afghan militants have created in the remote tribal areas.

U.S. officials have never publicly acknowledged the use of drone strikes against militants in Pakistan, but privately they have confirmed their existence to various news outlets.

Pakistan has condemned the attacks as a violation of its sovereignty, but the strikes are believed to be carried out with the help of Pakistani intelligence.