The United States has called on Turkey to end its state of emergency and safeguard the rule of law, following the re-arrest of the chairman of the local arm of Amnesty International.
US-Turkish relations have been strained recently by a series of disagreements, especially over the Syria crisis.
Taner Kilic was one of 11 human rights activists arrested last year on what Amnesty International has said were "bogus terrorism charges." He is the only one of the group still jailed after eight months in detention, the rights group said.
Mr Kilic was conditionally released last week, but the prosecution successfully appealed the decision and he was re-arrested before he had even arrived home, Amnesty said in a statement.
US State Department spokeswoman Heather Nauert said at a briefing that the United States was "deeply troubled" by Mr Kilic's re-arrest on February 1.
She said Washington was closely following Mr Kilic's case, as well as those against other human rights defenders, journalists, civil society leaders and opposition politicians detained in the state of emergency that followed a failed coup against President Tayyip Erdogan on July 15, 2016.
"We call on the Turkish government to end the protracted state of emergency, to release those detained arbitrarily under the emergency authorities and to safeguard the rule of law," Ms Nauert said, noting that the emergency had "chilled freedom of expression" and raised concerns about judicial independence.
Meanwhile on Wednesday a Turkish court sentenced 64 military academy officers and trainees to life in prison for involvement in the failed coup, the state-run Anadolu news agency said.
Another 100 defendants were acquitted in the case, it said.
Those sentenced were involved with plotters of the coup and had flown unsuspecting military academy trainees to a military headquarters to confront civilians opposing the attempted putsch, Anadolu said, citing the indictment.
Four of the sentenced were given "aggravated life" sentences, the harshest punishment possible under Turkish law because it raises the minimum required for parole. The four were found guilty of attempting to overthrow the constitutional order.
In the year after the coup, Turkey arrested more than 40,000 people and fired 125,000, including many from the police, army, and judiciary. Mr Erdogan blames the attempted coup on Fethullah Gulen, an exiled cleric and former ally based in the United States. Mr Gulen has denied any role in the plot.