Sunni religious leaders say they have decided to close down the sect's mosques in Baghdad indefinitely to protest attacks targeting clerics and worshippers, highlighting Iraq's deepening sectarian rift.

Sheik Mustafa al-Bayati, member of the Iraqi Doctrine Council where senior Sunni scholars sit to issue religious edicts, says the decision was taken on Thursday and came into effect on Saturday.

Sectarian violence has spiked in Iraq over the past seven months. The bloodiest attacks have targeted Shiites but Sunnis have also been killed in apparent reprisals.

On Friday, bombs targeted two Sunni mosques in Baghdad, killing four. And last week, gunmen killed a cleric as he was leaving a mosque in western Baghdad, police said.

It's unclear how far Sunnis have complied with the closure.