Seven persons were killed and five injured when motorcycle-borne gunmen opened fire on a bus carrying Shiite Muslims to a mosque in Karachi for Friday prayers, killing seven and injuring five others, police said.

The two gunmen carrying AK 47 guns fired at the bus using when it had stopped for a signal at a traffic intersection.

The victims were employees of a defence department research body Space and Upper Atmospheric Research Organisation (SUPARCO).

Police suspect it could be a sectarian terrorist attack as all the dead were minority Shia Muslims.

This was the second major attack on Shia Muslims after the recent attack on a mosque in Quetta, which resulted in the death of over 40 people. The dead included two suicide attackers. Police subsequently arrested five activists of Lashkar Jhangvi, a Sunni sectarian extremist outfit, which was banned by President Gen Pervez Musharraf.