A US-backed Syrian force confirmed on Friday that it had caught British Islamic State group fighter Alexanda Amon Kotey last month as he attempted to flee from Syria to Turkey.
"We captured some big commanders. One of them is Alexanda Kotey," Redur Khalil, a spokesperson and senior official in the Syrian Democratic Forces, told AFP in the northeastern town of Amuda.
"He was captured by an anti-terrorism unit on January 24 in the countryside near Raqa. He was trying to escape to Turkey in coordination with his friends and contacts on the Turkish side," he said.
The SDF spearheaded a four-month operation that culminated in mid-October last year with the retaking of Raqa, which had been the inner sanctum of the "caliphate" declared by IS in 2014.
That victory was the doom of the jihadist proto-state, the last pockets of which were then retaken within weeks by the SDF and other forces in Iraq and Syria.
Kotey was part of a four-member IS kidnapping cell dubbed "The Beatles" that was notorious for videotaping beheadings.
A US defence official on Thursday announced his arrest by the SDF, together with that of fellow Briton El Shafee el-Sheikh.
The pair are believed to have "participated in the detention, exploitation and execution of Western detainees," the official said in a statement.
A third IS member, Aine Davis, is being held in Turkey, while Mohammed Emwazi -- dubbed "Jihadi John" -- was killed in a 2015 coalition drone strike.
Redur Khalil could not confirm Sheikh's capture however, saying he had no information about the second British jihadist.
He said that Kotey was being interrogated but did not specify who by.
"He is being interrogated. We think that he was a member of a group that has been torturing foreign hostages," the Kurdish official said.
Last year, the US State Department said the London-born Kotey had "likely" taken part in executions and used "exceptionally cruel torture methods, including electric shock and waterboarding," while guarding the group's captives.