Police said on Sunday they believed local rivalry was behind the late Saturday blast at a minority Shia Muslim shrine in Fatehpur village, 350km south of Quetta.

The motive for the attack was unclear and investigators had not determined whether it was a suicide bombing.

"One body has been badly mutilated. We are looking at the possibility he was a suicide bomber or that he was trying to plant the bomb and mistimed or that he was just someone too close to the explosion," provincial police chief Chaudhry Muhammad Yaqub told The Associated Press.

The bomb went off at 10.20pm on Saturday as thousands of worshippers were taking supper at the shrine.

Pakistan has a history of sectarian violence between Sunni and Shia militants especially in the Baluchistan, the largest but poorest province, which has also been troubled recently by attacks by ethnic minority militants fighting for autonomy.