An American drone fired two missiles at a bakery in northwest Pakistan Saturday and killed four suspected militants, officials said, as the U.S. pushed on with its drone campaign despite Pakistani demands to stop. This was the third such strike in the country in less than a week.

Drone attacks in Pakistani tribal areas where Afghan and other militants have found refuge are considered a key tactic by U.S. officials in the war against al-Qaida and its Taliban supporters. But many Pakistanis resent the strikes, which they consider an affront to their sovereignty.

Two Pakistani intelligence officials said the latest attack took place in Miran Shah, the main town in the North Waziristan tribal region.

The officials said the victims were buying goods from a bakery when the missiles hit. Residents were still removing the debris, officials said. All of the dead were foreigners, but the officials did not have any information on their identities or nationalities.

The officials spoke on condition of anonymity because they were not authorized to talk to the media. The U.S. rarely talks publicly about the covert CIA-run drone program in Pakistan.

Drone strikes have become an increasingly contentious issue between Washington and Pakistan. Pakistan's parliament has demanded the U.S. end all attacks on its territory.

Some figures within the Pakistani government and military are widely believed to have supported the attacks in the past. Washington-Islamabad security cooperation has declined as relations between the two countries have deteriorated, but many analysts believe there is still some support for the attacks on militants within Pakistan's senior ranks.

U.S. officials have said in private that the strikes are a vital anti-terror tool and have killed many senior al-Qaida and Taliban commanders.

On Thursday, a suspected U.S. drone killed 10 alleged militants in northwest Pakistan near the Afghan border.

The attack took place in a militant hideout in the North Waziristan tribal area. Most of those killed were believed to be Uzbek insurgents.

On Wednesday four suspected militants were killed in the village of Datta Khel Kalai in North Waziristan.

The ongoing strikes have complicated negotiations between Islamabad and Washington about reopening supply routes for NATO troops in Afghanistan.

Pakistan closed the routes six months ago in retaliation for U.S. airstrikes that killed 24 Pakistani soldiers along the Afghan border. The Americans say the attacks were an accident.