Turkish authorities have detained a nephew of Fethullah Gulen, a US-based Muslim cleric accused of organising the failed military coup last week, according to state run media.
Gulen, who denies any involvement in the coup, has lived in self-imposed exile in the US since 1999 but has an extensive network of followers in Turkey and elsewhere.
His nephew Muhammed Sait Gulen was detained in Erzurum in northeastern Turkey, and will be taken to Ankara, the capital, for questioning.
Among possible charges that may be brought against him is membership of a terrorist organisation, state news agency Andalou reported.
Nearly 1,700 military personnel have been sacked and 130 media outlets shut down as the crackdown continues following the failed coup.
The dispatch comes after President Erdogan called on US to hand over cleric Fethullah Gulen, who he blames for Turkey's failed coup.
Turkey has been warned of the consequences of imposing the death penalty as punishment to those involved in the failed coup attempt.