Prominent Turkish rights activist and businessman Osman Kavala has been jailed pending trial, charged with seeking to overthrow the government, state-run Anadolu news agency reported on Wednesday.

An Istanbul court remanded Kavala in custody as part of an investigation into the movement of US-based cleric Fethullah Gulen, which Ankara accuses of carrying out an attempted coup in July last year, the agency said.

It said Kavala was charged with “attempting to overthrow the constitutional order” and “attempting to overthrow the government of the Republic of Turkey“.

Kavala, whose Anadolu Kultur organisation is involved in promoting culture and rights, was detained nearly two weeks ago at Istanbul’s Ataturk Airport, prompting expressions of concern from Europe and the United States.

Since the failed putsch on July 15, 2016, more than 50,000 people have been jailed as they face trial and some 150,000 sacked or suspended from jobs in the civil service and private sector.

The US State Department described Kavala’s initial detention as an example of a “very alarming trend” of detention of civil society leaders, journalists, academics and activists in Turkey.

The Turkish government says the measures are necessary due to the gravity of the threats it faces. Gulen has denied involvement in last year’s attempted coup.