Pakistani authorities say two suspected Sunni militants blew themselves up after an intense firefight with police in the southwestern city of Quetta. The incident raises fears of violence, as Shi?ite Muslims prepare for their annual Ashura celebrations.

The police chief of Baluchistan province, Chaudhry Mohammad Yaqoob, says the alleged terrorists were planning a suicide attack against Sunday's annual Shi?ite procession.

Mr. Yaqoob says security forces, acting on a tip, raided the militants' hideout early Friday.

"They [the police] were fired at with automatic weapons,? he said.  ?They responded, and, in exchange of fire, they found out that, after some time, they [the militants] exploded themselves."

Mr. Yaqoob says the suspects' hideout was along the route of the Shi?ite procession marking Ashura, which commemorates the death of a grandson of the prophet Mohammed.

The authorities are trying to identify the bodies of the two extremists. Meanwhile, security in Quetta has been tightened.

Some reports say the militants were members of an outlawed Sunni extremist group, called Lashkar-e-Jhangvi.

Mr. Yaqoob says local police will step up security before Sunday's procession. Homes on the route will be searched, and the central government has been asked to put the army on alert, in case the provincial government needs help. The police chief says he is confident there will be no attacks.

The sectarian violence in Pakistan between extremists of the two Muslim sects has claimed hundreds of lives in recent years.

At least 44 people were killed in Quetta last year, when suspected Sunni Muslim militants attacked a Shi?ite mosque. In the previous year, 57 people died in a suicide attack on a Shi?ite procession.