The Pentagon was trying to confirm fresh reports Tuesday that ISIS leader Abu Bakr al-Baghdadi has been killed, as the terror group teeters on the brink of defeat in Iraq and prepares to make its final stand in the Syrian city of Raqqa.

The Syrian Observatory for Human Rights – which has had a good record in reporting ISIS news – and Iraq’s Al Sumaria News were the two outlets primarily reporting the most-wanted terrorist’s death, with both citing sources inside ISIS. Baghdadi had been rumored to be killed numerous times since his rise to infamy as the so-called “Caliph” of ISIS-controlled territory – only for those reports to eventually be proven wrong. In June, Baghdadi was reportedly killed by Russian forces; however, no conclusive proof ever emerged of the Islamist’s death.

Adding to the speculation, President Trump tweeted ambiguously around 8:30 a.m. on Tuesday: “Big wins against ISIS!” It was unclear if Trump was referring to the possible death of Baghdadi or another event, such as the fall of ISIS-held Mosul to U.S.-backed troops.

Iraqi and Kurdish officials also were unable to confirm Baghdadi’s death to Reuters.

The Syrian Observatory for Human Rights linked its confirmation to a high-ranking ISIS source.

"[We have] confirmed information from leaders, including one of the first rank, in the Islamic State in the eastern countryside of Deir al-Zor," the director of the British-based war monitoring group Rami Abdulrahman told Reuters.

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ISIS leader Abu Bakr al-Baghdadi seen in 2014. (AP)

Al Sumaria said ISIS on Tuesday “announced in a very brief statement” that Baghdadi was dead and “talked about the announcement” of a successor. The Al Sumaria source also spoke of an internal coup brewing within ISIS, with hardcore Baghdadi supporters being arrested.

If Tuesday’s report is true, it was not immediately known how Baghdadi died or which country may have been responsible for his death.

ISIS hadn't confirmed Baghdadi's reported death via its propoganda arm.

Fox News’ Catherine Herridge contributed to this report.