Two aides of Iraq's most senior Shia cleric, Grand Ayatollah Ali al-Sistani, have been shot dead in separate incidents in southern Iraq.

The ayatollah's office said one of the men, Amjad al-Janabi, had been attacked after leaving a mosque near Basra on Thursday evening.

The other Ahmad al-Barqawi was shot as he drove home to the city of Diwaniya

The killings mean at least five aides of Ayatollah Sistani have been killed since June.

There has been no word on who might be behind the attacks, but correspondents say it could be related to a power struggle among Shia groups in southern Iraq.

In protest at the assassinations, Friday prayers were cancelled at mosques in southern Iraq controlled by Ayatollah Sistani, a representative of the cleric told AFP.

Ayatollah Sistani is a moderate and widely respected figure in Iraq.

PHOTO CAPTION

Man carried poster of Grand Ayatollah Ali al-Sistani