KABUL, Afghanistan - At least 34 people were killed and more than 130 injured Thursday in Afghanistan and Pakistan in sectarian violence that coincided with a Muslim holy day, especially revered among Shiites.

The day's attacks occurred in Pakistan's North-West Frontier Province, where hundreds of Shiites in the town of Hangu had turned out to participate in a procession marking Ashoura, which commemorates the martyrdom in 680 of Hussein, grandson of the prophet Muhammad.

Before sermons by clerics could begin, police said, at least one suicide bomber who may have been disguised as a mourner detonated himself. The blast killed at least 27 people and wounded approximately 30, according to the Interior Ministry director general, Brig. Javed Cheema.

Later in the day, it was reported that gunmen opened fire on a bus just outside the town, killing four.

In the past few years, Shiites in Pakistan - who are a minority - have been the victims of regular attacks thought to have been perpetrated by Sunni Muslim groups.

In Afghanistan, where about 80 percent of the population is Sunni, at least three people were killed and more than 100 injured when a clash erupted between Shiites and Sunnis in the city of Herat.