Angela Merkel on Tuesday demanded the release of German nationals being held in Turkey as she took a hard line on international relations just over three weeks before German elections.

In an uncharacteristically tough-talking performance, Mrs Merkel warned that Germany could block future EU cooperation with Turkey over the dispute.

The usually diplomatic German chancellor also lashed out at Poland, wading into a row with the EU over the independence of its judiciary.

“I would like to have better relations with Turkey, but we have to be realistic,” Mrs Merkel told her annual summer press conference in Berlin.