Islamabad, Pakistan: An apparent suicide bombing ripped through a Shiite Muslim procession Thursday in northwestern Pakistan, killing six people, injuring dozens and sparking riots during the Muslim sect's most important holiday, officials said.

Army troops took control of the town and a curfew was imposed as the Shiites responded by burning shops and cars in Hangu, about 200 kilometres southwest of the capital, Islamabad, district police Chief Ayub Khan said.

"We thought the bomb was detonated by remote control, but now it appears to be a suicide attack," Khan said.

Hangu is near Kohat, a major town in northwest Pakistan.

Police have been deployed in force across Pakistan for a number of days ahead of the Ashoura ceremony.

Many Shiites mark the ceremony by publicly wailing and by whipping themselves with knives attached to chains.