Abu Bakr al-Baghdadi, leader of Islamic State, is dead, according to a Syrian war monitor.

"(We have) confirmed information from leaders, including one of the first rank, in the Islamic State in the eastern countryside of Deir al-Zor," Rami Abdel Rahman, director of the UK-based Syrian Observatory for Human Rights said. "We learned of it today but we do not know when he died or how."

Russia's defence ministry said last month that it may have killed Baghdadi when one of its air strikes hit a gathering of Islamic State of Iraq and the Levant (Isil) commanders on the outskirts of the Syrian city of Raqqa, but the US said it could not corroborate the death and Western and Iraqi officials have been sceptical.