Grand Ayatollah Sayyed Mohammed Saeed al-Hakim, one of Iraq’s most senior and influential Muslim Shia clerics, has died of a heart attack at the age of 85, his family said.

A relative, Mohsen al-Hakim, told The Associated Press that al-Hakim died at the Al Hayat hospital in the southern holy city of Najaf on Friday, where he was taken after suffering a sudden heart attack.

His office announced that he died of a sudden medical condition.

Al-Hakim holds the highest theological title in Shia Islam – Ayatollah al-Uzma, which means Grand or Supreme Ayatollah.

He was seen as the top contender to succeed Iraq’s top Shia cleric, Ayatollah Ali al-Sistani, who is in his early nineties.

The Najaf-born cleric is a member of the well-known and highly respected Hakim family of Shia scholars.

His maternal grandfather is Mohsen Al-Tabataba’i Al-Hakim, a scholar and one of the most prominent thinkers of Shia Islam.

His father is Muhammad Ali al-Hakim, one of the most respected clerics in Najaf.

His second cousin, Sayyed Ammar al-Hakim leads the al-Hikma, or National Wisdom Movement, one of the largest Shia political parties in Iraq

Along with the Afghan-born Mohammed Ishaq al-Fayadh, Al-Hakim was seen as one of the most likely contenders to succeed al-Sistani, Iraq’s top Shia spiritual leader.

Iraq’s president and prime minister and other politicians issued statements eulogising Al-Hakim.

The US embassy in Baghdad tweeted its condolences, describing him as “a symbol of peace, love, and harmony across the region”.

Mohammed Saeed al-Hakim was exposed from early on to an education that focused on jurisprudence and religious studies and had some of the most prominent clerics among his teachers. He soon turned to teaching and became one of the leading Shia scholars in Najaf.

Like most Shia religious leaders in the holy city, he was put under house arrest during the last days of Iraqi dictator Saddam Hussein’s rule, before the US invasion of Iraq.

Al-Hakim was among a group of three top Shia leaders who were threatened with death by a rival Shia cleric shortly after Hussein was toppled in 2003.

He was targeted in an attempted assassination in 2003, when his house in Najaf was bombed. Three of al-Hakim’s bodyguards were killed, and members of his family were injured.

Al-Hakim himself came away from the blast with minimal injuries. Relatives blamed terrorists for the bomb, which was hidden in a gas cylinder.

He is one of four Grand Ayatollahs who teach at the Hawza, the religious seminary of Najaf. He has written many books and publications, some of which were translated into several languages.

Al-Hakim is survived by a wife and eight children.