Officials in Pakistan's northwest Kurram tribal region say a suicide bomber on a motorcycle has blown himself up at a busy market, killing at least 26 people.

Authorities say the blast in the town of Parachinar, near the Afghan border, happened near a mosque in a busy market, around the time of Friday prayers. The attack wounded more than 50 people and destroyed several shops. Local reports say the bombing targeted Shi'ite Muslims.

Authorities said police later shot and killed three more people who were protesting the attack. A curfew has been imposed in the town to prevent more protests.

A local Taliban splinter group claimed responsibility for the attack, according to Fazal Saeed, who said he was the group's leader. He told reporters the attack was retaliation for Shi'ite attacks on Sunni Muslims in the area.

The Kurram tribal agency is home to a sizable Shi'ite population in a country dominated by Sunni Muslims. The area has been the scene of suicide attacks and other sectarian violence, mostly engineered by Sunni militants, including the Taliban and al-Qaida.

In nearby Khyber tribal region, security officials say Pakistani troops killed 17 pro-Taliban militants Friday in a joint operation with a government-backed local militia. One soldier and three militiamen were also reported to have died in the operation, which targeted a local Taliban group known as Lashkar-e-Islam.