Clashes between Taliban militants and security forces killed 51 people, including 47 militants in a volatile region on the border with Afghanistan, officials said.

Fighting is spreading across Pakistan's northwest as the government tries to crack down on Taliban and al-Qaida fighters blamed for attacks in Afghanistan and Pakistan.

On Monday, pro-government tribesmen exchanged fire with militants in the Nawa and Kotkai areas of Bajur, tribal elder Nazi Jan said. Thirteen militants and two pro-government tribesmen were killed, he and Khan said.

In another part of northwest, a local leader of a pro-government secular political party and four aides were wounded in a roadside bombing in Upper Dir, said police official Shah Faisal. All were in stable condition, he added.

British officials covered up evidence that a Taliban commander killed by special forces in Helmand last year was in fact a Pakistani military officer, according to highly placed Afghan officials.

The commander, targeted in a compound in the Sangin valley, was one of six killed in the past year by SAS and SBS forces. When the British soldiers entered the compound they discovered a Pakistani military ID on the body.

It was the first physical evidence of covert Pakistani military operations against British forces in Afghanistan even though Islamabad insists it is a close ally in the war against terror.