Mullah Mohammad Abdullah was the chief prayer leader of a central mosque in Islamabad and was on his way home from a nearby mosque when he was hit by several bullets fired from a passing car. He died in hospital.

Hundreds of his supporters took to the streets in protest, burning vehicles and throwing stones.

Police have not ruled out a sectarian motive behind the assassination. There is now a heavy police presence in the area.

In the past sectarian killings of this kind have been followed by retaliatory murders.

More violence than usual

The BBC's Owen Bennet-Jones says the current level of sectarian violence seems more intense than usual.

The death of the cleric follows the killing of another Sunni religious leader in Islamabad last month. Also last month, four leaders of a militant Sunni group were shot and killed in another hit-and-run attack in Islamabad.

Sectarian violence has in the past been confined to the Punjab.

The BBC's Zaffar Abbas in Islamabad said the recent spate of killings in the capital was posing a major security challenge for Pakistan's prime minister.