The UK-based Syrian Observatory for Human Rights said Wednesday that sources had told its monitors that a March 4 airstrike targeting Shishani's convoy killed his bodyguards and "seriously injured" the commander.

"He did not die," Observatory Director Rami Abdurrahman said.

The strike itself involved waves of jets and drones targeting a suspected militant convoy near al-Shadadi in northeastern Syria, US officials said.

On Tuesday, an official in the Syrian Kurdish YPG militia, which has been battling IS in the al-Shadadi area, said it had received information that Shishani was killed but offered no further details.

US officials had confirmed that the raids targeted Shishani, with one saying on condition of anonymity that the Georgian national had been "likely killed" in the attack.

Who is Shishani?

Born in 1986 in Georgia, then part of the Soviet Union, the red-bearded militant nicknamed "Omar the Chechen" has a reputation as a close military adviser to Islamic State leader Abu Bakr al-Baghdadi, who was said by followers to have relied heavily on Shishani.

US officials have referred to the militant as the equivalent to the group's "secretary of defense" and placed a $5 million (4.56 million-euro) bounty on his head.

Shishani comes from the Pankisi Gorge region of Georgia that is populated mainly by ethnic Chechens. He battled Russia as a militant before joining the Georgian military in 2006, and fought Russian forces again during Georgia's five-day war over South Ossetia in 2008.

He resurfaced in northern Syria in 2012 as the leader of a battalion of foreign fighters, according to Aymenn Jawad Al-Tamimi, research fellow at the Middle East Forum, a US think tank.

'Most senior military commander' in IS

Richard Barrett of the US-based Soufan Group described him as IS's "most senior military commander," adding that he had led key battles.

"He is clearly a very capable commander and has the loyalty of Chechen fighters who are considered by ISIS as elite troops," Barrett told the AFP news agency.

Shishani is not a member of IS's political leadership, a structure that is even more opaque than its military command.

But the lack of a US presence on the ground makes it difficult to assess the success of operations targeting militants in Syria, and Shishani's death has been erroneously reported several times.

jar/msh (AFP, Reuters)