Pakistan has arrested dozens of suspected Islamic militants following two recent sectarian bomb attacks.

Officials say more than 50 members of outlawed Sunni and Shi'ite militant groups have been detained in several cities in Punjab province.

Also Saturday, two leading Sunni clerics were shot dead in Karachi, when gunmen fired on their car.

Pakistani officials have feared escalating sectarian violence between radical Sunni and Shi'ite Islamic groups after recent bombings on members of the two sects killed more than 70 people.

The bombings sparked protest rallies in which supporters of militant groups vowed revenge for the attacks. This week the government announced it was banning such religious gatherings except in mosques in order to prevent future attacks.