A US drone on Tuesday fired three missiles at a militant compound in Pakistan's northwestern tribal belt near the Afghan border, killing six militants, officials said.

"At least six militants were killed and five others were wounded when a US drone fired three missiles at a militant compound," a senior security official told AFP.

The attack took place in Azam Warsak village, some 25 kilometres (15 miles) west of Wana, the main town in South Waziristan tribal district, the official said.

An intelligence official and a South Waziristan administration official confirmed the attack and death toll to AFP via phone in Miranshah, the capital of neighbouring North Waziristan tribal district.

Another security official in Peshawar, the capital of Khyber Pakhtunkhwa province also confirmed that the unmanned US aircraft killed at least six militants.

Some 15 US drone attacks have taken place in just 18 days in North Waziristan.

US missile strikes have killed about 100 militants since September 3 in the rugged tribal belt, which Washington has branded a global headquarters of Al-Qaeda and the most dangerous spot on Earth.

Over 1,100 people have been killed in more than 130 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.

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 missiles have mostly targeted militants linked with the Haqqani network, based in North Waziristan.

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.

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