Updated

A suspected U.S. missile attack killed six alleged militants in Pakistan just over the border from Afghanistan on Wednesday, intelligence officials said, the third such strike on the Al Qaeda and Taliban stronghold in 24 hours.

There were reports the brother of the new head of the Pakistani Taliban was among those killed in the strikes, though a spokesman for the militant group said he died in a gunbattle with troops.

Americans officials have said they are considering increasing the frequency of airstrikes in the region.

Unmanned drones have carried out more than 70 missile strikes in northwestern Pakistan over the last year in a covert program, killing several top militant commanders along with sympathizers and civilians. The Pakistani government publicly protests the attacks but is widely believed to sanction them and provide intelligence for at least some.

Wednesday's strike destroyed a vehicle close to the town of Mir Ali in North Waziristan, killing six suspected militants inside, said two intelligence officials who spoke on condition of anonymity in line with the secretive nature of their work.

Attacks Tuesday in North and South Waziristan killed 12 people, officials said. A witness said another strike hit the area late Monday, but no one was killed.

Washington says defeating insurgents in Pakistan is vital for stabilizing Afghanistan, where violence is raging eight years after the U.S.-led invasion toppled the Taliban. The U.S. believes much of the Afghan insurgency is directed by militants in safe havens across the border.

American officials have said they are considering a strategy of intensified drone attacks against Al Qaeda and Taliban targets in Pakistan, part of an alternative to sending more troops to Afghanistan in what is an increasingly unpopular war.

While three drone strikes in 24 hours is unusual, it is not unprecedented for the U.S. to launch a series of missile attacks in a short span.

Also Wednesday, a Taliban spokesman said the brother of the new head of the Pakistani Taliban was killed in a shootout with troops close to the Afghan border. Local media reports, however, quoted intelligence sources as saying Kalimullah Mehsud was among several militants to die in one of the drone strikes late Tuesday.

Kalimullah's brother, Hakimullah Mehsud, took over the leadership of the Taliban in late August following the slaying of Baitullah Mehsud in a missile strike on Aug. 5. Video obtained by The Associated Press on Wednesday showed the body of the bearded former Taliban chief with his eyes closed and cuts on the right side of his face.

The death of Kalimullah — himself a ranking commander — was a fresh blow to the Taliban, which analysts say is still struggling to regroup following the death of Baitullah.

"I confirm he was among those martyred, but his sacrifice will make our movement stronger," Qari Hussain, a spokesman for the group, told The Associated Press by telephone from an undisclosed location.

With accurate information hard to come by and both the Taliban and the government not averse to engaging in propaganda, there has been much speculation over the group's leadership structure following the death of Baitullah.

Interior Minister Rahman Malik has said in the past he believed Hakimullah was dead and being impersonated by Kalimullah, apparently to project an image of strength to the movement's followers. The Taliban have denied that.