Ukraine's security service said on Friday it had detained the deputy of Abu Omar al-Shishani, the man the Pentagon described as Islamic State's "minister of war", after he crossed into Ukraine on a fake passport last year.
The SBU security service said it had taken into custody Al Bara Shishani, a Georgian citizen, in a joint operation with Georgia's Interior Ministry and the US Central Intelligence Agency (CIA).
An SBU statement said an examination of a photograph of Al Bara Shishani in the agency's possession "proved that the detained foreigner is indeed a wanted leader of Islamic State".
Georgia's state security service confirmed Al Bara Shishani was being held in Ukraine. "Yes, we can confirm this fact ... His (birth) name is Cezar Tokhosashvili," said Vika Klimicheva, a spokeswoman for the state security service.
He joined ISIS in 2015 and was the deputy to Abu Omar al-Shishani, who was killed in combat in 2016 and ranked among America's most wanted militants under a US programme that offered up to $5 million for information to help remove him from the battlefield.
Both men were born in Georgia's mountainous Pankisi gorge region.
After his death, Al Bara Shishani crossed into Turkey and later Ukraine where he continued to coordinate the activities of ISIS, the SBU statement said.
He was detained in the Kiev region near a private home where he resided, it added, without giving the date of the arrest.
According to Rami Abdel Rahman, the head of the Britain-based Syrian Observatory for Human Rights war monitor, Al Bara Shishani was not however a high-ranking ISIS figure but "a simple fighter".
The Georgian security service gave his real name as Cezar Tokhosashvili and said he was wanted as "a member of a terrorist organisation".