The Iraqi Health Ministry said Sunday that more than 621 people suffered from suffocation due to a chlorine gas leak in the Shiite holy city of Karbala.

In a brief statement, the ministry said that all affected individuals received medical treatment at hospitals in the city, located about 110 kilometers south of Baghdad.

Major Abbas al-Zaidi from the Karbala police told Xinhua that the leak occurred early Sunday at a drinking water treatment plant near the city, caused by a technical malfunction.

"Ambulances and civil defense teams immediately responded and sent them to local hospitals," Al-Zaidi said, noting that most of the cases ranged from mild to moderate.

According to al-Zaidi, the majority of those affected were Shiite pilgrims traveling on foot to Karbala to participate in the annual major ritual of Arbaeen.

Arbaeen marks the end of the 40-day mourning for Imam Hussein, the grandson of Prophet Muhammad, who was killed in the battle of Karbala in 680 AD.