Pakistani intelligence officials say a suspected U.S. drone strike has killed five people in the country's northwest, near the border with Afghanistan.

Intelligence officials say the drone fired four missiles early Wednesday on a suspected militant compound in the North Waziristan tribal agency.

The identities of those killed is not yet known, but the region is a stronghold of the al-Qaida linked Haqqani network and the Taliban.

Pakistan has repeatedly criticized drone attacks as illegal and a violation of its sovereignty, but U.S. officials say the strikes are an important tool in defeating the insurgents.

The attack comes just days after Pakistani opposition politician Imran Khan led a convoy of some 500 vehicles in an unprecedented march toward Taliban territory to protest CIA-led drone strikes.

The Haqqani network is blamed for a number of high-profile attacks in Afghanistan, including assaults last year on the U.S. Embassy in Kabul, NATO headquarters, and a coalition base.

The U.S. has been pressing Pakistan to launch a military offensive in North Waziristan, but the Pakistani army has said its forces are stretched too thin to target militants in the tribal agency.

U.S. and Pakistani officials in August confirmed a drone strike killed the day-to-day operations commander of the Haqqani network, Badruddin Haqqani.