By Saud Mehsud
DERA ISMAIL KHAN, Pakistan (Reuters) - Sectarian violence spread in Pakistan on Monday after clashes between minority Shi'ite and majority Sunni Muslims near the capital Islamabad prompted the government to impose a curfew and block mobile phone services over the weekend.
Clashes confined to areas in and around the capital at the weekend spilled over on Monday into two towns in the volatile northwest.
Tensions are high this month as Shi'ites mark Muharram, an annual period of mourning which has often sparked bouts of violence.
Rawalpindi, a garrison city near Islamabad, remained under curfew and tight security for three days after a Shi'ite procession on Friday degenerated into sectarian clashes which killed at least eight people.
On Monday, a mob set shops on fire in a predominantly Shi'ite district in the northwestern town of Kohat in clashes that killed a policeman and a civilian, police said.
Tensions were high in the northwestern city of Hangu, also subject to a curfew, local media reported.
During Muharram, a period of mourning to mark the death of Imam Hussein, a grandson of the Prophet Mohammed, Shi'ites hold long processions where they flagellate, beat or cut themselves to show their grief.
The authorities imposed a mobile phone blackout on Rawalpindi, the seat of the Pakistani army, and parts of Islamabad over the weekend. The curfew was lifted only on Monday, but the city remained tense.
Attacks on Pakistan's Shi'ites, who make up about a fifth of the 180 million population, have worsened in recent years.
Most of the attacks are the work of Sunni extremists affiliated with banned groups, such as the Taliban or Lashkar-e-Jhangvi, which wants to drive all Shi'ites out of Pakistan.
Hundreds of Shi'ites were killed in bombings and other attacks last year, including children gunned down on their way to school and doctors heading for work.
(Reporting by Syed Raza Hassan Writing by Maria Golovnina; Editing by Ron Popeski)