At least 55 people were killed yesterday in violence in Pakistan's troubled northwestern tribal region of Kyhber, which borders Afghanistan, local officials said.

Twenty-two people were killed in a suicide attack targeting a mosque after Friday prayers in the Tirah valley, while at least 10 soldiers and 23 Islamist militants died in an earlier clash around 10 kilometres away.

Kyhber is a haven for militants linked to the Pakistani Taliban and the threat of renewed fighting there between the army and insurgents prompted some 18,000 people to flee their homes in October last year.

Local administration official Jamilur Rehman told AFP that the suicide blast killed at least 22 people and wounded more than 20 others, adding the toll may rise.

"The bomber detonated himself near the gate of a mosque in Tirah valley of Khyber tribal region when people were returning from the prayers," he said.

The mosque is located in an area controlled by warlord Mangai Bagh, he said, adding that most of the dead were from his Lashkar-i-Islam — a group widely linked to militants and criminal gangs.

Earlier, at least 10 Pakistani soldiers and 23 militants were killed in a gunfight in the Tirah valley.

"At least 10 soldiers embraced martyrdom and three others were wounded," a senior security official told AFP, adding that the fighting lasted for nearly six hours.

"All law enforcement agencies' posts in the area were intact and the situation was stable,” the official said, blaming the Lashkar-i-Islam group for attacking the outpost.

Pakistan's seven tribal districts near the Afghan border are rife with home-grown insurgents and are strongholds of Taliban and al-Qaeda operatives.

Islamist militants have killed more than 4,900 people across Pakistan since government troops raided an extremist mosque in Islamabad in July2007.