Militants opened fire on a Shiite Muslim mosque where worshippers were gathering for Friday prayers, and then a suicide bomber detonated his explosives inside, killing 15 people in the latest attack aimed at the minority sect, police said, according to The Associated Press.

The attack hit the city of Peshawar, which is on the outskirts of Pakistan's tribal area, the main sanctuary for Islamic militants. They have targeted the city with scores of bombings in recent years.

Three militants initiated the attack on the mosque, located inside a Shiite religious school, by firing on a policeman who was standing guard outside, said senior police official Shafiullah Khan. The policeman was critically wounded, Khan said.

The militants then entered the mosque, where one of them detonated his suicide vest. The other two militants escaped, and police have launched a search operation to find them, Khan said. Fifteen people were killed and scores more wounded, he said.

Zawar Hussain, who was inside the mosque when the attackers struck, said their firing set off panic among the roughly 300 worshippers inside. Then came the explosion.

No one has claimed responsibility for the bombing.

Radical Sunni Muslims who consider Shiites to be heretics have stepped up attacks against the minority sect in Pakistan over the last several years.