European Commission President Jean-Claude Juncker called on Turkey Wednesday to "let our journalists go" following its arrests of French and German media personnel under a broad human rights crackdown.

Juncker also called on Turkey's leaders to stop insulting their EU counterparts as "fascists and Nazis" and said its disregard for the rule of law ruled out its membership in the bloc for the "foreseeable future."

But Juncker saved his strongest words for the fate of German and French journalists, during his annual state of the union speech to the European parliament in Strasbourg. 

"Journalists belong in newsrooms not in prisons. They belong where freedom of expression reigns," Juncker said. "I appeal to the powers that be in Turkey, let our journalists go!" 

In recent months, Turkey has arrested two French journalists on terror charges for allegedly supporting Kurdish militants, but later released one of them. 

Imprisoned in February, the correspondent of German daily Die Welt Deniz Yucel has been personally accused by President Recep Tayyip Erdogan of working as a "terror agent".

The European journalists are among more than 50,000 people who have been arrested in Turkey under the state of emergency imposed after last year's foiled coup to oust Erdogan.

According to the P24 press freedom group, there are 170 journalists behind bars in Turkey, most of whom were arrested after the coup.

Juncker also came to the defence of German Chancellor Angela Merkel whose government Erdogan accused of behaving like Nazis after German authorities blocked Turkish ruling party rallies ahead of a referendum in Turkey in April.

Many expatriate Turks work in Germany.

"Stop insulting our member states by comparing their leaders to fascists and Nazis," Juncker said. 

"Europe is a continent of mature democracies. Insults create roadblocks," the former Luxembourg premier said.

"Sometimes I get the feeling Turkey is intentionally placing these roadblocks so that it can blame Europe for any breakdown in accession talks," he said.

"As for us, we will always keep our hands stretched out towards the great Turkish people and those who are ready to work with us on the basis of our values," he said.

Turkey, like other accession candidates, "must give the rule of law, justice and fundamental rights utmost priority," Juncker said.

"This rules out EU membership for Turkey for the foreseeable future," he said.

The worsening tensions with Turkey have raised concerns over the fate of a deal struck with the EU last year that has helped stem the flow of hundreds of thousands of refugees and migrants into Greece.