The world's most wanted man was last seen in Mosul in 2014, announcing the birth of IS's much-feared "caliphate" across swathes of Iraq and Syria -- but appears to have outlived the Islamic proto-state.

In the video released Monday by IS's Al-Furqan media outlet, the man said to be Baghdadi referred to the months-long fight for IS's final bastion Baghouz, which ended in March.

"The battle for Baghouz is over," he said, sitting cross-legged on a cushion and addressing three men whose faces have been blurred.

He referred to a string of IS defeats, including its onetime Iraqi capital Mosul and Sirte in Libya, but insisted the jihadists had not "surrendered" territory.

"God ordered us to wage 'jihad.' He did not order us to win," he said.

In a segment in which the man is not on camera, his voice referred to the April 21 Easter attacks in Sri Lanka, which killed 253 people and wounded nearly 500, as "vengeance for their brothers in Baghouz".

The man said to be Baghdadi insisted IS's operations against the West were part of a "long battle," and that IS would continue to "take revenge" on members who had been killed.

"There will be more to come after this battle," he said.

- 'The Ghost' -

The video is filmed in a whitewalled room lined with cushions, but it was unclear exactly where or when the footage was shot.

The man in the video had a long grey beard that appeared dyed with henna and spoke slowly, often pausing for several seconds in the middle of his sentences.

He was identified as Baghdadi by both the SITE Intelligence Group, which tracks IS, and Hisham al-Hashemi, an Iraqi expert on the group.

But the US-led coalition, which has backed operations in both Iraq and Syria to defeat IS, said it was still trying to "independently corroborate the validity of the video posted today reportedly showing Abu Bakr al Baghdadi."

Born Ibrahim Awad al-Badri in 1971, Baghdadi was a passionate football fan who came from modest beginnings in Samarra, north of Baghdad.

After US-led forces invaded Iraq in 2003, he was detained in the American-run Camp Bucca, where is believed to have come of age as a jihadist.

He later rose through the ranks of Iraq's Al-Qaeda franchise and eventually took the helm in 2010, expanding into Syria in the midst of that country's war in 2013.

The following year, Baghdadi declared himself "caliph" of IS's sprawling territory in an infamous sermon from Mosul's famed Al-Nuri mosque.

He then lay low for years, earning him the nickname "The Ghost" amid repeated reports he had been killed or injured as IS's territory shrunk.

His last voice recording to his supporters was released in August, eight months after Iraq announced it had defeated IS and as the US-backed Syrian Democratic Forces closed in next door in Syria.

The SDF at the time said it did not believe Baghdadi was in Syria.

The United States has a $25-million US bounty on his head.