Those killed in Monday's attack are said to be Taliban fighters.

"Four militants were killed," a local government official said, requesting anonymity. He said the number of wounded was not immediately known.

A security official, however, said four people were wounded.

Witness accounts

After the attack, villagers say they heard a loud explosion and saw smoke rising from the area.

Two witnesses told the Associated Press news agency that the missile hit a vehicle with blacked-out windows.

Akhtar Rasool, a resident of Mir Ali, said the missile appeared to have struck a fighters' vehicle.

In depth


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Inside Story: Pakistan's military
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Monday's drone attack was the third within a week in North Waziristan, where fighters linked to Taliban and al-Qaeda are said to have sanctuaries.

At least 13 people died in a similar attack in North Waziristan last week when two missiles targeted a compound used by the Taliban.

Most of the operations have taken place in North and South Waziristan.

Since August 2008, nearly 60 such raids have killed more than 550 people.

The US is the only country in the region known to have the ability to launch missiles from drones, which are controlled remotely.

The US normally does not comment on suspected drone attacks.

Pakistan officially objects to the raids by US pilotless aircraft, saying they are a violation of its sovereignty and cause civilian casualties which bolster support for the fighters.