BEIRUT (REUTERS) - The suspected leader of an Al-Qaeda-linked militant group that claimed responsibility for bombing the Iranian embassy in Beirut two months ago died in custody on Saturday, security sources said.

Majid bin Muhammad al-Majid, a Saudi national who was wanted by authorities in his own country, had been suffering from kidney failure and went into a coma on Friday, the sources said.

He died in a military hospital in Beirut, they added.

Majid was believed to be the leader of the Abdullah Azzam Brigades, which have claimed attacks across the region, most recently the double suicide assault on Iran's Beirut embassy, which killed at least 25 people.

His identity was confirmed by Lebanese officials on Friday after DNA tests.

In tweets at the time of the bombing, the Abdullah Azzam brigades threatened more attacks in Lebanon unless Iran pulled its forces out of Syria.

An increasingly sectarian civil war there has attracted Sunni and Shi'ite Muslim fighters from neighbouring countries as well as military support and economic aid from Iran.

Last year Azzam Brigades, named after an associate of the late Al-Qaeda leader Osama bin Laden, were formally designated by the United States State Department as a foreign terrorist organisation.

The State Department said the group was divided into two branches: the Yusuf al-'Uyayri Battalions, named after a founder of Yemen-based Al-Qaeda in the Arabian Peninsula; and the Lebanon-based Ziyad al-Jarrah Battalions, named after one of the airliner hijackers who attacked New York and Washington on Sep 11, 2001.