The European Union and the United States have expressed alarm at Turkey's response to the failed coup, insisting the country must uphold democracy and human rights as it pursues those behind the plot.
At a joint news conference with US Secretary of State John Kerry, EU foreign policy chief Federica Mogherini said the incident "is no excuse to take the country away from fundamental rights and the rule of law, and we will be extremely vigilant on that".
Mr Kerry said Turkey must "uphold the highest standards for the country's democratic institutions and the rule of law".
While he recognised the need to apprehend the coup plotters, Mr Kerry added: "We caution against a reach that goes beyond that."
The pair spoke after a meeting in Brussels that also included the bloc's 28 foreign ministers, and after a weekend when Turkey's government responded to the coup attempt by rounding up some 7,500 people, including hundreds of judges and prosecutors.
In Berlin, Chancellor Angela Merkel's spokesman said talks on Turkey's bid to the join EU would end if Ankara restores the death penalty.
Her spokesman Steffen Seibert said "the institution of the death penalty can only mean that such a country could not be a member" of the bloc.
Both Ms Mogherini and Mr Kerry reiterated the trans-Atlantic support for Turkish President Recep Tayyip Erdogan's democratically-elected government.
But they illustrated deepening frustration with the Erdogan government's response to the failed coup, which has even included allegations by ministers of US complicity in the violence.
Meanwhile, the EU commissioner leading negotiations with Turkey on its bid to join the union has suggested Mr Erdogan is exploiting the crisis to eliminate opponents who may or may not have been involved in the coup.
"It is exactly what we feared," Johannes Hahn said.
It appears, he added, as if Turkey had "prepared" arrest lists of political opponents and was waiting for the right time to act.