Baghdad, Dec 11 (IANS): Iraq's Shia cleric Moqtada al-Sadr has ordered his followers to prepare for jihad against the Islamic State (IS) Sunni militant group who are reportedly preparing for an attack on the city of Samarra, an official said Thursday.

"Our brothers the Mujahedeen in the Peace Brigades must be ready to meet the call of jihad within 48 hours," said Abu Du'aa al-Issawi, al-Sadr's assistant for jihad affairs.

Earlier, Sadr called on his followers to form a new militia of "Peace Brigades" to protect Iraq's shrines and holy sites as the IS claimed the northern and central parts of the country, Xinhua reported.

The predominantly Sunni city of Samarra, some 120 km north of Baghdad, is home to the Shia shrine of Imam Ali al-Hadi.

The shrine contains the tombs of Ali al-Hadi and his son Hassan al-Askari, the 10th and 11th of the Shias' 12 most revered Imams.

On Feb 22, 2006, the Samarra shrine, also called the Golden Mosque, was hit by a bomb attack in which its 100-year-old Golden Dome was badly damaged.

In 2007, insurgents again bombed two minarets of the shrine.

The attacks sparked killings between Shiite and Sunni communities that claimed the lives of thousands of Iraqis.