The Pakistan police have arrested eight Shiite Muslims in connection with last month's attack on a Kentucky Fried Chicken restaurant that killed six employees, official sources said on Thursday.

On May 31, Angry Shiites had set fire to the KFC restaurant to protest a suicide bomb attack at Madinatul Ilm Imambargah mosque in Karachi. The protestors also damaged cars, shops and three gas stations.

Police officer Nabeejullah Khan said dozens of Shiites were detained during the violence. "We suspect eight of them (Shiites) were involved in the attack," he said, adding that the judge has given permission to keep the men under police custody for a week for interrogation.

Officers recovered explosive materials used to make bombs, two grenades and a pistol from the spot.

On May 30, a suicide bomber and two assailants attacked the mosque killing five -- two attackers, two guards and a worshipper. Police arrested two suspected Sunni militants on suspicion of involvement in the attack.

Pakistan has a history of sectarian violence, mostly blamed on rival majority Sunni and minority Shiite extremist groups. About 80 per cent of Pakistan's 150 million people are Sunnis and 17 per cent Shiites.

The schism between Sunnis and Shiites dates back to the 7th century and involves a dispute over who was the true heir to the prophet Muhammad.