PESHAWAR: Three people were shot dead Sunday and nine wounded in gun and grenade attacks Sunday in a northwestern Pakistani town troubled by sectarian violence, police said.

In the first attack, gunmen travelling on a motorcycle opened fire on two Shiite Muslim men in the main bazaar of Dera Ismail Khan town before fleeing the scene, local police officer Naimatullah Khan said.

"The victims who died on the spot were brothers. They belonged to the Shiite community," he told AFP.

Hours after the shooting a man hurled a grenade at a shop near a Sunni Muslim mosque injuring four people, said Ashiq Saleem, a senior official at the local hospital. Police officers confirmed the attack.

The incident triggered tensions and shops and markets were closed in the area of Dera Ismail Khan near the mosque, residents said.

Later Sunday in the town, a gunman opened fire on people shopping at a vendor's stall, Khan said, killing one man and wounding five others from the majority Sunni sect.

Dera Ismail Khan district, which borders Pakistan's restive tribal region, is a flashpoint for violence between the minority Shiite and majority Sunni communities.

Shiites account for some 20 percent of Pakistan's mostly Sunni Muslim population of 160 million.

Although the two groups usually coexist peacefully, more than 4,000 people have died in outbreaks of sectarian violence since the late 1980s.