The Islamic State (ISIS) group chief Abu Bakr al- Baghdadi is still alive and leading the terrorist group, the Pentagon on Friday said.

Baghdadi has always kept a low profile and the last confirmed sighting of Baghdadi was in Mosul, soon after ISIS captured the city. Baghdadi has since then released several audio messages urging fighters to fight on. He recently released another audio tape in the wake of the Mosul battle, asking his supporters to defend the city of Mosul.

Abu Bakr al-Baghdadi is more wanted than ever before with a whopping $25 million on his head

It is, however, not clear whether the ISIS chief is in Mosul or not where the US-backed Iraqi army is battling the ISIS militants to retake the major city, which is a stronghold of the terrorist group.

"We do think Baghdadi is alive and is still leading ISIL and we are obviously doing everything we can to track his movements. If we get the opportunity, we certainly would take advantage of any opportunity to deliver him the justice he deserves...We're doing everything we can. This is something we're spending a lot of time on," Pentagon spokesperson Peter Cook told CNN.

The United States more than doubled the bounty on Baghdadi earlier this month to $25 million. The reward on the ISIS chief has placed him in the category, which has only one other occupant, the leader of al-Qaeda Ayman al-Zawahiri.

The State Department's "Rewards for Justice Program" in 2011 had offered an initial bounty of $10 million for the elusive militant. The ISIS has taken control of swathes of Syria and Iraq and according to a US "Wanted" poster have "gained the allegiance of jihadist groups and radicalised individuals around the world, and has inspired attacks in the United States."

"Under al-Baghdadi, ISIL has been responsible for the deaths of thousands of civilians in the Middle East, including the brutal murder of numerous civilian hostages from Japan, the United Kingdom, and the United States," the State Department said.

"The group also has conducted chemical weapons attacks in Iraq and Syria in defiance of the longstanding global norm against the use of these appalling weapons, and has enabled or directed terrorist attacks beyond the borders of its self-declared caliphate," the department added.