A suicide bomber detonated his explosive vest outside a mosque in a Shia neighbourhood today in Pakistan's northwestern Kurram tribal region, killing at least 26 people, government officials said.
Three more people were killed when police shot at protesters from the Shia community after the bombing in Parachinar, the main town in Kurram, an official said.
A curfew was imposed in the town.
The bomber struck outside the mosque in a busy market after Friday prayers, in the latest attack by Sunni militants against minority Shias.
Kurram, the only part of Pakistan's border region that has a significant Shia population, has been racked by sectarian violence between Sunni and Shia tribes.
The Taliban and al-Qaeda's virulent anti-Shia ideology has meant years of bloody fighting.
Fazal Saeed, leader of a breakaway faction of the Pakistani Taliban, claimed responsibility for the latest attack in Kurram, near the Afghan border.
"We have targeted the Shia community of Parachinar because they were involved in activities against us," he told Reuters by telephone from an undisclosed location.
"We also warn the political administration of Parachinar to stop siding with the Shia community in all our disputes."
Shia Muslims are a minority sect of Islam, arising from a dispute over the successor to the Prophet Mohammad 1,400 years ago. Many extreme Sunni Muslims consider them apostates.
Saeed was part of the Tehrik-e-Taliban Pakistan (TTP) but broke away last year after disputes with the umbrella militant group's leadership.
He is said to have close ties with the Haqqani militant group, one of the most feared factions of the Afghan Taliban.
The TTP, al-Qaeda, and the Afghan Taliban movement fighting Western forces in Afghanistan are entrenched in Pakistan's northwestern tribal areas. All have been involved in anti-Shia activities for years.
They continue to have strongholds in the region despite a series of military operations in the last few years.
Pakistan's army and air force have been conducting operations against militant groups in Kurram since the beginning of the year. Dozens have been killed in fierce fighting this month.
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