ISIS Leader Abu Bakr al-Baghdadi Fled Mosul, Now Moving Between Iraq and Syria: Officials

ISIS leader Abu Bakr al-Baghdadi makes a public appearance at a mosque in Mosul, Iraq, according to a video posted online on July 5, 2014. Reuters/Social Media Website via Reuters TV

The elusive leader of the Islamic State militant group (ISIS), Abu Bakr al-Baghdadi, has fled the northern Iraqi city of Mosul, according to U.S. and Iraqi officials.

Baghdadi reportedly left the city before Iraqi coalition forces, backed by air power, encircled the extremist group's biggest territorial hold.

"He [Baghdadi] was in Mosul at some point before the offensive," an unidentified U.S. official told AFP. "We know he's been there."

"He left before we isolated Mosul and Tal Afar," the official added, referring to a town that lies to the west of the city.

Baghdadi delivered his first sermon as the group's caliph and self-proclaimed leader of the world's Muslims, from the city, announcing the creation of the caliphate that would stretch from Syria to Iraq.

An Iraqi official, speaking on condition of anonymity, confirmed to Newsweek that Baghdadi was no longer in Mosul, but now moves across the Iraqi-Syrian border in some of the largely lawless areas where the group retains control in both countries.

"He moves between al-Hajin in Syria and al-Ba'aj in Iraq," the official said.

Read more: Don't Kill, ISIS Leader Baghdadi. Capture Him

The U.S.-led coalition believes Baghdadi has now left the battle for the city in the hands of his commanders, and is not likely to play a significant factor in combat tactics. "He probably gave broad strategic guidance and has left it to battlefield commanders," the U.S. official said.

But letters from the group's leadership to commanders in other ISIS-held bastions, such as the northern city of Manbij, which it eventually lost in August last year, point to tactical orders from above. The group's War Committee in Raqqa, its de facto capital, told top ISIS commander in Manbij, Abu Yahya al-Shami, to execute defecting fighters, quash dissent in its ranks and imprison "bewitched" militants. The general message was: Fight to the last.

The U.S. is leading the extensive search for Baghdadi, the world's most wanted extremist, having dispatched a ground expeditionary force to capture or kill members of the group's leadership. Coalition airstrikes have also targeted Baghdadi, with several reports of life-changing injuries to the ISIS leader and his temporary replacement while he recovered.

Mosul and Raqqa represent ISIS's biggest prizes, and the group continues to cling on to large areas in both cities. In Mosul, however, Iraqi security forces have captured the eastern part of the city, and have launched a new offensive on western parts.

As the battle progresses, Kurdish and Arab ground forces, as well as the U.S. and allied partners such as Turkey, have discussed preparations to recapture Raqqa.

But neither the capture of Baghdadi nor victory in Mosul or Raqqa would signal the end of ISIS, the U.S. official said. The coalition estimates that around 15,000 ISIS militants remain in ISIS-held territory.

"Raqqa would probably not be the final battle against ISIS...There is still ISIS in the rest of the Euphrates river valley downstream that will have to be dealt with."