A barrage of US missiles killed at least 15 militants in Pakistan's North Waziristan tribal district on Tuesday, obliterating compounds and vehicles used by Islamist fighters, officials said.

Pakistani security officials reported the strikes in what is reputedly the country's most impregnable Taliban and Al-Qaeda fortress where US officials want Pakistan to launch a ground offensive to eliminate the militant threat.

They said the first strike destroyed two compounds and killed five rebels in Ghulam Khan village, 20 kilometres (13 miles) east of Miranshah, the main town in North Waziristan.

They reported that further strikes carried out by unmanned aircraft killed 10 militants minutes apart in Nawab village on the border with Afghanistan.

"At least 10 people were killed when US drones fired missiles at three vehicles," one senior security official told AFP.

"First a US drone fired missiles at a double-cabin pick-up truck and about 15 minutes later two more cars were struck," he added.

The areas targeted are strongholds of the Taliban- and Al-Qaeda-linked Haqqani network, one of the most potent US foes in Afghanistan, particularly in eastern mountain districts near the porous border with Pakistan.

Neither the identities of those killed on Tuesday, nor whether they included any high-value targets, were immediately clear.

The Haqqani leadership is based in North Waziristan. The group was created by Afghan warlord Jalaluddin Haqqani and run by his son Sirajuddin.

Taliban, Pakistani warlord Hafiz Gul Bahadur and his ally Maulvi Sadiq Noor also have fiefdoms in North Waziristan.

US officials say they are active in escalating a nine-year insurgency in Afghanistan, putting up a deadly fight against 140,000 US-led NATO troops there and seeking to bring down the Western-backed government in Kabul.

Washington says wiping out the militant threat in Pakistan's semi-autonomous tribal belt is vital to winning the war against the Taliban in Afghanistan and defeating Al-Qaeda.

The United States does not confirm drone attacks, but its military and the Central Intelligence Agency operating in Afghanistan are the only forces that deploy the unmanned aircraft in the region.

The covert campaign has this year doubled missile attacks in the tribal area, where around 100 drone strikes have killed more than 650 people since January 1, compared to 45 killing 420 people in 2009, according to an AFP tally.

Pakistan tacitly cooperates with the bombing campaign, which US officials say has severely weakened Al-Qaeda's leadership, but has stalled on launching a ground offensive in North Waziristan, saying its troops are overstretched.

Pakistani security officials reported that 15 to 21 militants were killed in US missile attacks in North Waziristan on Monday.

Around 4,000 people have died in suicide and bomb attacks across Pakistan since government forces raided an extremist mosque in Islamabad in 2007. The attacks have been blamed on networks linked to the Taliban and Al-Qaeda.