A suicide attack at a Shia mosque in the Pakistani city of Peshawar has left 10 people dead and at least 20 wounded, officials have said.
The mosque was crowded at the time of the blast
The blast came as the minority Shia community prepared to mark this weekend's Ashura festival.
An eyewitness told the BBC the teenage bomber pushed past security personnel before blowing himself up.
Security has been high in Pakistan during the holy month of Muharram, of which Ashura marks the climax.
A BBC reporter at the scene counted five bodies and was told by officials other dead had been removed.
History of violence
Local police chief Imtiaz Khan said 10 people died. The mosque was crowded with worshippers at the time of the blast.
There has been no claim of responsibility for the attack
Officials said the attacker blew himself up outside the mosque gates after being stopped by police.
But eyewitness Ghulam Abbas told the BBC Urdu service: "I saw a young man push past security personnel and rush into the mosque and then he blew himself up... there was a big blast and smoke everywhere."
Another witness was Arshad Ali, whose brother died in the blast, the Associated Press news agency reports.
He said: "People present there tried to stop him. He took out a pistol, shot three times and then blew himself up."
There has been no claim of responsibility for the attack.
Pakistan has a history of violence between Sunni and Shia extremists.
Thursday's bombing happened in the same area of Peshawar where 11 people died in a suicide attack last year during Ashura.
Ashura is the culmination of Muharram, marking the seventh century death of the Prophet Muhammad's grandson, Imam Hussein, an event which led to the split in Islam between the Shia and Sunni sects.
Last week a suicide blast killed more than 20 people at a police checkpoint in the eastern city of Lahore but it is not clear if that attack was sectarian.
The latest attack comes as Pakistan heads for elections on 18 February.
The polls were delayed by six weeks after the assassination of opposition leader Benazir Bhutto, a secular politician who had vowed to tackle militants.
North West Frontier Province, of which Peshawar is the capital, is the scene of frequent clashes between security forces and militants allied to the Taleban movement, active in neighbouring Afghanistan.