A U.S. drone strike Thursday killed five commanders of a powerful Pakistani Taliban faction that attacks Western forces in Afghanistan, one of the group's leaders told Reuters.

The Obama administration has stepped up drone strikes against al-Qaida and Taliban militants in Pakistan's tribal border areas in an effort to stabilize Afghanistan before the end of 2014, when all NATO combat troops are due home.

The dead commanders belonged to the Maulvi Nazir faction of Pakistan's Taliban, which carries out cross-border attacks from its strongholds in South Waziristan.

The group threatened in June to escalate attacks on U.S.-led NATO troops in Afghanistan in response to intensified drone strikes on its territory.

Four of the commanders killed by the remotely-piloted drone were identified as Hazrat Omar, Nazir's younger brother, Khan Mohammad, Miraj Wazir and Ashfaq Wazir. The group did not name the fifth.

Local intelligence officials said three Nazir commanders were killed. The reports could not be independently verified.

They are a very important group because while they are based in Pakistan they are very active in Afghanistan, said Mansur Khan Mehsud of the FATA Research Centre think tank.

If you look at drone strikes, they are one of the most heavily targeted groups.

U.S. drones have killed high-profile al Qaeda and Taliban leaders in Pakistan's restive tribal regions, where everyone from al Qaeda to the Taliban to Arab fighters train and plan attacks.

The New America Foundation think tank estimates at least 325 militants were killed in U.S. drone strikes in Pakistan this year.

Pakistani leaders say drone strikes inflame widespread anti-American sentiment in Pakistan and play into the hands of militants.

But analysts say high-profile militants can't be spotted without help from Pakistani intelligence.

The latest attack comes nearly a week after U.S. Secretary of State Hillary Clinton visited Islamabad accompanied by high-level U.S. military and intelligence officials.

Clinton again urged Pakistan to eliminate what Washington says are safe havens along its porous border with Afghanistan.

Nazir's group of around 1,200 fighters is among the militants not opposed to the Pakistani state. Pakistan struck a deal with the faction in 2007 under which they would not harbor anti-government militants.

In exchange, the group would not be targeted by the military when offensives began against the Pakistani Taliban.

(Additional reporting by Hafiz Wazir in Wana and Saud Mehsud in Dera Ismail Khan; Writing by Qasim Nauman; Editing by Michael Georgy)

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