A volley of US missile strikes killed 25 militants after destroying their compounds in Pakistan's lawless tribal areas on the Afghan border, security officials said Tuesday.

Twin drone attacks hit militant strongholds in North and South Waziristan 12 hours apart, as the United States announced it was suspending more than a third of its annual military aid to Pakistan, bringing relations to a new low.

Early Tuesday, a US drone fired two missiles at a compound in South Waziristan's Bushnarai area, a senior security official told AFP.

Several missile strikes have recently targeted hideouts in the area, considered a stronghold of Pakistani Taliban commander Mullah Nazir, he said.

Late Monday, at least 12 militants were killed when US drones fired four missiles on a compound and a vehicle in the Gorwaik area of Datta Khel town, in North Waziristan. Reports of up to 16 militants killed could not be confirmed.

"In last night's drone strike, at least 12 militants were killed and six others were wounded, and in today's strike the death toll has risen to 13. Two were wounded," a security official told AFP Tuesday.

Intelligence officials in Miranshah, the capital of North Waziristan, said foreigners were among those killed in the second attack.

Pakistani officials use the term "foreigners" for Al-Qaeda-linked Arab, Central Asians and other non-Pakistani fighters.

Washington has called Pakistan's semi-autonomous northwest tribal region the most dangerous place on Earth and the global headquarters of Al-Qaeda.

The United States does not officially confirm Predator drone attacks, but its military and the CIA operating in Afghanistan are the only forces that deploy the armed, unmanned aircraft in the region.

But the covert missile programme is deeply unpopular in Pakistan, where anti-American sentiment and relations with the United States have nosedived since US troops killed Osama bin Laden in the town of Abbottabad on May 2.

Although Pakistani politicians united to demand an end to drone strikes after US Navy SEALs entered Pakistan, seemingly without knowledge of the government or military, to kill the Al-Qaeda leader, they have continued.

A total of 21 US drone strikes have been reported in Pakistan's tribal belt since May 6, killing around 130 militants, according to local officials.

White House chief of Staff William Daley confirmed in a television interview on Sunday that the United States had decided to withhold almost a third of its annual $2.7 billion security assistance to Islamabad.

The bin Laden raid humiliated the Pakistani military and invited allegations of incompetence and complicity, while Washington has increasingly demanded that Islamabad take decisive action against terror networks.

Pakistan hit back by saying it was capable of fighting without US assistance, although analysts doubt the aid cuts will encourage commanders to open fresh fronts -- as long demanded by the United States.

"The army in the past as well as at present has conducted successful military operations using its own resources without any external support whatsoever," military spokesman Major General Athar Abbas told AFP.

In suspending aid, analysts said the United States is showing it will no longer give the benefit of the doubt to Pakistan's military after a long debate on how to handle it and where its loyalties lie.

"This is a high-stakes gamble in a way -- that somehow this is going to get the military to wake up to the fact that their long dependence on the United States, for equipment in particular, could end," said Marvin Weinbaum, scholar-in-residence at the Middle East Institute.