One of Iraq’s top Shia leaders, Abdul-Aziz Al-Hakim, died of lung cancer on Wednesday in Tehran, at a time when Iraq is threatened with fresh political instability.

Mr. Al-Hakim was the head of the Supreme Islamic Iraqi Council (ISCI) since 2003, after his brother, Grand Ayatollah Muhammad Baqer Al-Hakim, was killed in a deadly car bombing in Najaf.

On Thursday, Mr. Al-Hakim’s body was flown for burial from Tehran to the Iraqi city of Najaf, which has an iconic spiritual status in Shia Islam. In his tribute, Iran’s Supreme Leader, Ayatollah Ali Khamenei described the passing of Mr. Al-Hakim as “a big loss for the Iraqi people and government,” and “a painful incident for the Islamic Republic [of Iran].”

Hundreds of Iranians gathered in front of the Iraqi embassy in Tehran on Thursday to bid farewell to the Iraqi cleric.

Mr. Al-Hakim’s ISCI is currently part of Iraq’s ruling Shia alliance, which includes the Dawa party of Nouri Al-Maliki, the Prime Minister. Several senior ministers in the government belong to ISCI, which exercises substantial influence inside Iraq’s security establishment. The organisation has special ties with Iran, to which its top leaders migrated during the eight-year Iran-Iraq war, fought in the 1980’s.

Analysts say ISCI has been close to the Islamic Revolutionary Guard Corps (IRGC) of Iran, which helped train the Badr Corps, ISCI’s combat affiliate.

Mr. Al-Hakim was diagnosed with lung cancer at a Texas hospital in the United States, after which he visited Iran for chemotherapy, prior to his hospitalisation. His son, Ammar Al-Hakim is expected to be ISCI’s next leader, at a time that the political landscape of Iraq is changing rapidly.

Earlier this week, it was announced that ISCI will become part of the Iraqi National Alliance (INA), the new Shia dominated combine. Moqtada Al-Sadr, a young cleric who has been consistent in his defiance of the United States occupation of Iraq, and has been residing in the Iranian city of Qom since 2007, along with the secular Ahmad Chalabi are the other heavyweights in the new alliance. Mr. Maliki, the Prime Minister, has so far not joined the new coalition.

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