Q+A - What is behind U.S. drone attacks in Pakistan?

(Reuters) - A missile-firing U.S. drone aircraft killed eight Islamist militants in northwest Pakistan on Friday, Pakistani officials said.

It was the second U.S. drone strike in the North Waziristan region on the Afghan border since late on Wednesday and comes as the United States weighs options for how to deal with an intensifying Taliban insurgency in Afghanistan.

The U.S. Central Intelligence Agency operates the missile-firing Predator and Reaper drones. Here are some questions and answers about the strikes:

WHY DOES THE UNITED STATES ATTACK?

Many al Qaeda and Taliban members fled to northwestern Pakistan's ungoverned ethnic Pashtun belt after U.S.-led forces ousted Afghanistan's Taliban government in 2001. From their sanctuaries there, the militants have orchestrated insurgencies in Afghanistan and Pakistan. The United States and Afghanistan have pressed Pakistan to eliminate the sanctuaries. Apparently frustrated by Pakistan's inability to do so, the United States itself is hitting the militants. One option being considered as the United States reviews its Afghan strategy is for more missile attacks in Pakistan.

HOW MANY ATTACKS?

The United States has carried out 46 drone air strikes in northwestern border regions this year, killing about 415 people, including many foreign militants, according to a tally reports from Pakistani officials and residents. In 2008, there were 32 strikes, 24 of them in the last four months of the year, that killed about 240 people. U.S. attacks on the Pakistani Taliban in their South Waziristan stronghold picked up after the Pakistani government ordered a military offensive against them in June. But there have been no missile strikes in South Waziristan since the Pakistani army launched the offensive on Oct. 17.