The alleged military head of the "Islamic State" (IS) terror group was arrested in Turkey, a police statement said on Sunday.
Codenamed Basim, the Afghan national has been dubbed the right-hand man of dead IS leader Abu Bakr al Baghdadi.
Basim was detained in a suburb of Istanbul and had been traveling on a fake passport, according to the police statement.
Basim had reportedly disappeared months after the terrorist group was overrun in Syria and Iraq in December 2017.
Photo of balding, bearded man
Turkish media published a photograph of a balding, bearded man in a light coat following the arrest and an earlier image, purportedly of the same person, showing a long-haired, heavily bearded man in military fatigues wielding a curved sword.
The Demiroren news agency said Basim was suspected of organizing training for IS while in Syria and Iraq, as well as serving on its decision-making council.
NTV reported that Basim was being interrogated after a joint operation by the National Intelligence Organization (MIT) and Istanbul's police force.
IS leader Baghdadi killed himself in October 2019 by detonating a suicide vest during a US-led raid on his hideout in Syria's northwestern Idlib province.
Turkey regularly detains IS suspects, many allegedly planning attacks in the country.
With material from The Associated Press