The international coalition, led by the US, cannot confirm Tuesday's announcement by a British-based monitoring group that claimed that the leader of the Islamic State Abu Bakr al-Baghdadi had died, but hopes that it was true.

"Despite all the helpful reports to us from every source imaginable, I'm unable to confirm or deny either where he is or whether he is alive or dead. Let me just say for the record my fervent hope is it is the latter," Lt. Gen Stephen Townsend told a news briefing from Baghdad via video conferencing.

In an email statement to Efe news agency, US Army Col. Joe Scrocca, director of public affairs for the Combined Joint Task Force, said: "We cannot confirm this report, but hope it is true. We strongly advise (the) IS to implement a strong line of succession, it will be needed." 

However, the colonel said that he strongly urges the IS to apply a strong line of succession, as it will be necessary.

The Syrian Observatory for Human Rights had published a brief statement earlier on Tuesday on Facebook reporting the claims.

"Confirmed information for the Syrian Observatory for Human Rights about the death of Abu Bakr al-Baghdadi," the statement said.

With his last media appearance in 2014 in the Iraqi city of Mosul, al-Baghdadi's death has been reported on several occasions but never confirmed.

The London-based group did not mention whether al-Baghdadi had lost his life in a Russian bombing at the end of May, as Russian officials in June claimed.

On June 16, the Russian defence ministry said al-Baghdadi might have died on May 28 during Russian airstrikes in the northern Syrian city of al-Raqqa, the IS main stronghold in the war-torn country.

At that time, the US could not confirm the announcement made by Russia as it seemed to have several weaknesses.

The Islamic State is currently pulling out of both Syria and Iraq, where Iraqi Prime Minister Haidar al-Abadi announced on Monday the complete liberation of the northern city of Mosul.