Missiles fired by US drones in two attacks Tuesday killed 15 militants in Pakistan's tribal badlands, with 11 strikes targeting the lawless Afghan border area in 11 days, officials said.

In the first attack, officials said, four missiles hit a compound in Bushnarai village in Shawal district of North Waziristan, where Al-Qaeda-linked and Taliban fighters have carved out strongholds beyond government control.

"Eleven militants were killed in today's drone attack," a senior Pakistani security official in the area told AFP on condition of anonymity, updating an earlier toll for the first attack.

He described the area as a stronghold of Arab militants and said there were reports that "foreigners" -- a term for Al-Qaeda operatives in Pakistan -- were among the dead but said the nationalities of the dead had not been confirmed.

Another security official confirmed that the remains of 11 people had been pulled out of the compound's wreckage.

US drones carried out low-level flights in different areas of North Waziristan, including Shawal where the first strike took place this morning, the second security official told AFP.

Shawal district is more than 300 kilometres (190 miles) from Pakistan's capital Islamabad, headquarters of the country's civilian government.

The area is a stronghold of Pakistani Taliban warlord Hafiz Gul Bahadur and is populated by Arab fighters.

The second drone attack took place in Qutabkhel village in the outskirts of Miranshah on Tuesday evening, killing four militants, officials said, bringing the day's toll to 15.

"A US drone fired two missiles on a vehicle carrying militants outside Miranshah," a senior security official told AFP.

"At least four militants were killed in the attack," the official said, adding that the identities of the militants were not immediately known.

A fresh surge in US missile strikes has killed 64 militants since September 3 in Pakistan's northwestern tribal belt, which Washington has branded a global headquarters of Al-Qaeda and the most dangerous spot on Earth.

With Pakistan struggling to cope with devastating floods that have hit 21 million people in the country's worst humanitarian disaster, Islamist militant violence has picked up in recent weeks with a fresh series of major bombings.

The Taliban last week threatened Pakistani security forces with further suicide attacks to avenge US missile strikes, which have become a key tactic in the US-led fight to reverse a Taliban insurgency in neighbouring Afghanistan.

An Islamist militant bombing campaign has killed more than 3,700 people and fanned instability across nuclear-armed Pakistan since July 2007.

Under US pressure to crack down on Islamist havens along the Afghan border, Pakistan has in the past year stepped up military operations against largely homegrown militants in the area.

Officials in Washington say the drone strikes have killed a number of high-value targets including Pakistani Taliban chief Baitullah Mehsud and help protect foreign troops in Afghanistan from attacks plotted across the border.

The US military does not as a rule confirm drone attacks, but its armed forces and the Central Intelligence Agency operating in Afghanistan are the only forces that deploy pilotless drones in the region.

Over 1,070 people have been killed in more than 125 drone strikes in Pakistan since August 2008, including a number of senior militants. However, the attacks fuel anti-American sentiment in the conservative Muslim country.

Al-Qaeda announced in June that its number three leader and Osama bin Laden's one-time treasurer Mustafa Abu al-Yazid had been killed in what security officials said appeared to be a drone strike in North Waziristan.