Discreet in his youth and invisible as the world's most wanted man, Abu Bakr al-Baghdadi was once again reported dead on Tuesday as his cross-border “caliphate” falls apart.

The reclusive militant chief's death was confirmed by “top tier commanders” from the militant Islamic State (IS) group, the Syrian Observatory for Human Rights claimed.

The 46-year-old Iraqi, nicknamed “The Ghost”, has not appeared in public since he delivered a sermon at Mosul's famed Nuri mosque in 2014, declaring himself “caliph”. His attempt to build a militant state has since faced major setbacks.

Iraq has declared victory over the militants in Mosul. That defeat followed the loss of swathes of territory in Iraq and in Syria, where US-backed forces are pressing an assault on the militants' stronghold Raqa.

Baghdadi has been rumoured wounded or killed several times in the past. While he was said to have left Mosul earlier this year, his whereabouts were never confirmed.

Introvert

Keeping a low profile — in contrast to slain Al-Qaeda leader Osama bin Laden — helped Baghdadi to survive for years despite a $25 million US bounty on his head.

Ibrahim Awad al-Badri came from modest beginnings to became the overlord of a militant state ruling millions of inhabitants. He was born in Samarra, north of Baghdad.

His high school results were not good enough for law school and his poor eyesight prevented him from joining the army. So he moved to Baghdad to study Islam, settling in the neighbourhood of Tobchi.

After US-led forces invaded Iraq in 2003, he founded his own insurgent outfit.

It never carried out major attacks, however, and by the time he was arrested in February 2004 and detained at the US military's Camp Bucca, he was still very much a second or third-tier militant.

Strategist

The prison in southern Iraq was where he started showing signs of leadership. He was released at the end of 2004 for lack of evidence. Iraqi security services arrested him twice subsequently, in 2007 and 2012, but let him go because they did not know who he was.

In 2005, he pledged allegiance to Abu Musab al-Zarqawi, the brutal leader of the local Al-Qaeda franchise.

Zarqawi was killed by an American drone strike in 2006. After his successor was also eliminated, Baghdadi took the helm of the group in 2010.

He revived the militant Islamic State of Iraq (ISI), later declaring it independent of Al-Qaeda, expanding into Syria in 2013 then launching a sweeping offensive across northern Iraq in 2014.

'Rapist'

Baghdadi had grown up in a family divided between a religious clan and officers loyal to Saddam Hussein's secular Baath party.

Years later, his militant organisation was to incorporate ex-Baathists, capitalising on the bitterness many officers felt after the American decision to dissolve the Iraqi army in 2003.

That gave his leadership the military legitimacy he personally lacked and formed a solid backbone of what was to become IS, combining extreme religious propaganda with ferocious guerrilla efficiency.

Uncharismatic and an average orator, Baghdadi was described by his repudiated ex-wife Saja al-Dulaimi, who now lives in Lebanon, as a “normal family man” who was good with children.

He is thought to have had three wives, Asma al-Kubaysi, Isra al-Qaysi — from Iraq and Syria — and another, more recently, from the Gulf.

He has been accused of repeatedly raping girls and women he kept as sex slaves, including a pre-teen Yazidi girl and the US aid worker Kayla Mueller, who was subsequently killed.