A US drone on Monday fired two missiles at a vehicle carrying militants in Pakistan's northwestern tribal area, near the Afghan border, killing five rebels, officials said.

The strike occurred at Khar Qamar, a village in Datta Khel area, and was the fourth drone attack the past four days, a senior security official in the area told AFP.

"The US drone fired two missiles at the militants' vehicle, killing five rebels," he said.

He said nationalities of the militants killed in the strike were not immediately known.

A senior local administration official also confirmed the strike and casualties.

US forces have been waging a drone war against Taliban and Al-Qaeda-linked commanders in Pakistan's northwestern tribal belt, where militants have carved out havens in mountains outside direct government control.

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.

Washington has branded the rugged tribal area on the Afghan border -- part of which has now been hit by Pakistan's catastrophic flooding -- a global headquarters of Al-Qaeda and the most dangerous place on Earth.

More than 1,040 people have been killed in 121 drone strikes in Pakistan since August 2008. However, the attacks fuel anti-American sentiment in the conservative Muslim country.

Officials in Washington say the strikes are a vital tool needed to protect the more than 140,000 foreign troops in Afghanistan, and have killed a number of high-value targets including Pakistani Taliban chief Baitullah Mehsud.

Under US pressure to crack down on Islamist havens along the Afghan border, Pakistan has in the past year significantly increased operations against militants in the area.

Last year Pakistan launched its most ambitious military offensive yet against Taliban militants in South Waziristan, expanding the campaign to many of the other seven semi-autonomous tribal districts along the border.

Pakistani commanders have not ruled out an offensive in North Waziristan, but argue that gains in South Waziristan and the northwestern district of Swat need to be consolidated to prevent their troops from being stretched too thin.

Waziristan came under renewed scrutiny when Faisal Shahzad, a Pakistani-American charged over an attempted bombing in New York on May 1, allegedly told US interrogators he went to the region for terrorist training.

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.