Mohammed Abdul Kadir remains on the run following the bludgeoning of Jalal Uddin in an attack in Rochdale.
On Friday, Mohammed Hussain Syeedy, 21, was convicted of murdering the 71-year-old after driving Mr Kadir to the scene of the killing. He was jailed for life.
An international warrant has been issued for the arrest of Mr Kadir.
Syeedy, of Ramsay Street, Rochdale, acted as a getaway driver but Manchester Crown Court heard Mr Kadir is thought to have used a hammer to deliver the fatal blows.
Det Ch Supt Tony Mole, of the North West Counter Terrorism Unit, said: "Mr Kadir left the country before he was declared a suspect.
"We are working very closely with all our international partners to trace him. If we can find him we will bring him lawfully back to the UK, where he will stand trial."
The trial heard Mr Uddin was "brutally" killed because he practised taweez faith healing, regarded by extremists as "black magic".
The prosecution said Mr Kadir, of Chamber Road, boarded a flight from Manchester to Copenhagen, Denmark, on 21 February and from there flew to Istanbul.
His whereabouts are unknown although it is thought he may have travelled onwards to Syria, the jury was told.
Murder of an imam - the interpretation of 'magic'
Mr Uddin's son, Saleh Al-Arif, said he will be greatly missed.
"My father was the greatest man in our lives. His smile will never be replaced," he said.
"They say perfection cannot be achieved, but my father came close, as demonstrated by his principles, his mannerisms and his incredible love for his family and his religion."
Police have vowed to hunt down a suspected Islamic extremist thought to have fled to Syria following the murder of an imam in Greater Manchester.