Los Angeles (AFP) - National Basketball Association (NBA) player Enes Kanter, an outspoken critic of Turkish President Recep Tayyip Erdogan, said on Friday his father had been arrested in Istanbul and could face torture.

"My father is arrested because of my outspoken criticism of the ruling party," Kanter wrote on his website. "He may get tortured for simply being my family member."

The Oklahoma City Thunder centre, who had voiced support for Muslim cleric Fethulla Gulen in Twitter postings after an attempted putsch last July aimed at ousting Erdogan, said thousands in Turkey could face similar fates for their support of the Gulen-inspired Hizmet, which he calls a social initiative advocating for human rights.

Turkey, meanwhile, accuses US-based Gulen of ordering the failed coup and refers to the movement as the "Fethulla Terrorist Organisation".

Kanter's family has publicly denounced the player's support of Gulen.

The pro-government Anadolu news agency reported Friday that Mehmet Kanter had been placed in protective custody in connection with an inquiry targeting Gulen.

The arrest came a week after a warrant was issued for Enes Kanter, whose passport has been cancelled by Turkish authorities.

Kanter, who has compared Erdogan to Adolf Hitler, was briefly detained in Romania on May 20 but returned to the United States with his green card, telling reporters he wanted to seek US citizenship.