ISTANBUL (Reuters) - Turkish police detained 20 suspected Islamic State militants thought to be of Central Asian and North African origin in the Aegean coastal city of Izmir on Wednesday, according to a police statement.

The suspects were understood to have traveled to Izmir from the central city of Konya, the statement said. Security forces are hunting for a gunman who killed 39 people in an Istanbul nightclub on New Year's Day, an attack claimed by Islamic State.

The gunman is still at large. Turkish media reports have said the assailant was believed to have spent time in Konya before coming to Istanbul and carrying out the attack.

(Writing by Humeyra Pamuk; Editing by Nick Tattersall)