Suspected U.S. missiles slammed into a training camp ran by Pakistani Taliban leader Baitullah Mehsud on Tuesday, killing at least 12 militants in the latest in a flurry of strikes against him and his followers, intelligence officials said.

The attack took place in the Makeen area of South Waziristan close to the Afghan border, four officials told The Associated Press on condition of anonymity because they were not authorized to speak to media. The missiles were believed launched by unmanned American planes.

"Our initial reports from agents in the field say at least 12 to 14 Taliban have died in today's American missile attack," said one official, adding several militants were also wounded. Mehsud was not among the victims, the officers said.

The United States has launched more than 40 missile strikes against targets in the border area since last August.

Tuesday was the fourth in two weeks against Mehsud and his followers in his stronghold of South Waziristan.

Pakistan's army is deploying troops in South Waziristan and launching regular air strikes of its own to try and kill or capture Mehsud, who is blamed for organizing many of the bloodiest suicide attacks in Pakistan over the last few years.

Washington does not directly acknowledge the attacks. Because the insurgents conduct their training and staging operations in outlying towns and villages, some civilians have died in the attacks, prompting protests from some local Pakistani officials.

Islamabad officially protests the strikes as violations of its sovereignty, but most experts believe the government secretly endorses them and likely provides the United States with intelligence on possible targets.