Kutbettin Gulen detained in Izmir province as part of ongoing crackdown on people alleged to be behind July events.
Some followers of Muslim leader and businessman Fethullah Gulen were involved in last summer’s failed coup in Turkey, a UK Parliament report says, adding that there is no evidence to suggest the Gulen Movement as a whole was behind the plot.
The Foreign Affairs Committee’s (FCO) report released on Saturday said the evidence of individual Gulenists’ involvement in the attempt to overthrow the government was “mostly anecdotal or circumstantial, sometimes premised on information from confessions or informants”.
The report also said that such evidence “is so far inconclusive in relation to the organisation as a whole and its leadership”.
Since the July 15 coup attempt, Turkey has accused Pennsylvania-based Gulen of being behind the push to overthrow President Recep Tayyip Erdogan.
During the failed coup, about 300 people, the vast majority of them civilians, were killed across Turkey as rebel soldiers targeted the government by bombing state buildings.
“The FCO knows too little for itself about who was responsible for the coup attempt in Turkey, or about the ‘Gulenists’ … whom the Turkish government exclusively blames for the coup,” the report said.
“We found that the Turkish government’s account of the Gulenists and the coup, which the FCO seems willing to accept broadly at face value, is not substantiated by hard, publicly available evidence, although as yet uncontradicted by the same standard.”
The report cited a “lack of transparency”, adding that it was unlikely Gulenists were the only elements involved in the coup.
Turkey is seeking Gulen’s extradition from the US, a request which has not been granted.
As well as accusing Gulen’s network of staging the coup attempt, Turkey says it is behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police and judiciary.
The FCO said that while Turkey faced a threat following the coup attempt against the backdrop of increased “terrorism”, it disagreed with some tough measures by the Turkish government under a state of emergency.
“Turkey is an important strategic partner facing a volatile period,” said Crispin Blunt, chair of the Foreign Affairs Committee.
“It needs and deserves our support, but that support needs to include our critique where Turkish policy is not in its own, or our joint long-term interests: these are regional security and stability as well as strong and accountable institutions in Turkey.”