Top Islamic State commander leader Omar al-Shishani, known as Omar the Chechen, was "seriously injured" in a recent US strike in Syria but not killed, a monitoring group said Wednesday, after a US official said the militant had "likely died" in the attack.

The Britain-based Syrian Observatory for Human Rights said that according to its sources the March 4 strike had indeed targeted the jihadist's convoy, killing his bodyguards, but he himself "was seriously injured" and taken to hospital. 

"He's not dead," the Observatory's director Rami Abdel Rahman told AFP.