As an array of local and international forces close in on Islamic State's last redoubts in Syria and Iraq, the whereabouts of the extremist group's secretive leader remain a mystery.
A media outlet linked to the Syrian military reported Friday that Abu Bakr Baghdadi had been spotted in the eastern town of Bukamal during a recent offensive to recapture Islamic State's last urban stronghold in Syria. But Baghdadi sightings have been reported before. So has his death. None of it has ever been confirmed.
The latest claim was also carried by a media unit operated by the Lebanese Shiite militia, Hezbollah, whose forces took part in the operation in support of Syrian President Bashar Assad.
No further details were provided, however, including what the source was for the purported sighting.
The capture or killing of Baghdadi — who has a $25-million U.S. bounty on his head — would be another significant blow to Islamic State, which has lost more than 90% of the territory it once controlled in Syria and Iraq following multiple offensives on both sides of the border.
But Syrian opposition activists with contacts in the region were skeptical that Baghdadi was holed up inside Bukamal, where fierce clashes were reported Friday. They suggested that pro-Assad forces were trying to divert attention from an Islamic State counterattack that reclaimed as much of half of the border town after the government declared it liberated Thursday.
"This is propaganda," said Rami Abdul-Rahman of the supposed Baghdadi sighting. Abdul-Rahman is head of the pro-opposition Syrian Observatory for Human Rights, based in Britain. "If it's true, let them show the video."
The U.S.-led coalition fighting Islamic State in Syria and Iraq said it did not have any "verifiable information" concerning Baghdadi's whereabouts. Neither the coalition nor the Syrian militias it supports are operating in the immediate vicinity of Bukamal, it said in an email.
Rumors about Baghdadi have swirled since his fighters swept across Syria and Iraq in 2014, capturing about a third of both countries.
The cleric, known primarily through grainy mug shots and audio messages exhorting fellow Sunnis Muslims to rise up against "infidels," is believed to have made only one public appearance. In July 2014, he delivered a sermon at the Grand Mosque in the northern Iraqi city of Mosul in which he declared himself leader of a new caliphate, or Islamic state, stretching from Aleppo in Syria to Diyala in Iraq.
The mosque now lies in ruins, destroyed by Islamic State fighters before Iraqi forces, backed by U.S. air power, recaptured the country's second-largest city in July after a nine-month campaign.
Raqqah, the group's de facto capital in Syria, fell to a U.S.-backed alliance of Kurdish and Arab militias in September.
The militants are now concentrated in a string of Syrian villages along the Euphrates River and desert areas straddling the porous border between Syria and Iraq. It is here that Syrian and Iraqi commanders believe Baghdadi may be hiding.
Baghdadi, who took the reins of Islamic State in 2010, is a Baghdad-trained cleric from the city of Samarra who is reported to have fought against U.S. forces in Iraq after the 2003 invasion that toppled Saddam Hussein. He was a follower of the late Abu Musab Zarqawi, a Jordanian militant who led a branch of Al Qaeda in Iraq but fell out with the group over his bombing campaign against Shiite Muslims and gory beheading videos, which were considered too brutal even for Al Qaeda.
Security officials in Iraq and Syria have periodically stated that Baghdadi was injured or killed in strikes, but those claims were never verified or were later denied.
In June, the Russian Defense Ministry said there was a "high probability" that Baghdadi had been killed the previous month in a Russian airstrike on a meeting of Islamic State leaders outside Raqqah. The Syrian Observatory disputed Russia's account, saying its sources had confirmed Baghdadi's death, but reported the death had happened in neighboring Dair Alzul province.
U.S. Defense Secretary James N. Mattis and other senior Pentagon officials, however, later said they believed Baghdadi was still alive and U.S. forces would continue to search for him.
In September, Islamic State released a purported audio recording of its leader in which Baghdadi sought to rally his beleaguered troops, many of whom are now said to be surrendering to the advancing forces.
In the 46-minute recording, Baghdadi praised his fighters for waging a fierce defense of Mosul and focused on the continuing threat posed by Islamic State-inspired attacks in places as far away as London, Paris and San Bernardino.
"Now the Americans, the Russians and the Europeans are living in terror in their countries, fearing the strikes of the mujahedin," he said.