A man detonated an explosive belt at the external gate of the Mausoleum of Sayyid Muhammed bin Ali al-Hadi at around 11 pm, allowing several gunmen to storm the site and start shooting at worshippers on the occasion of the Eid al-Fitr festival, according to the security sources.
The site also came under rocket fire during the attack that was claimed by ISIS. The terror group said in a statement the attack was carried out by three suicide bombers wearing explosive belts.
Pictures posted on social media showed a fire burning in the market located at the entrance of the mausoleum. It was not clear if the site itself was damaged.
Prominent Shiite cleric Muqtada al-Sadr ordered his forces, the Peace Brigade, to deploy around the mausoleum, near Balad, about 93 kilometers (58 miles) north of Baghdad, Reuters reported.
A 2006 bombing destroyed the golden dome of the shrine of Ali al-Hadi and his other son, Imam Hasan al-Askari (AS).
The attack came several days after a massive bombing that killed at least 292 people in a mainly Shiite shopping area of central Baghdad, in the deadliest single bombing since the US-led invasion that toppled Saddam Hussein in 2003.