EU chiefs want to meet Erdogan at NATO summit: Merkel

European Union Commission President Jean-Claude Juncker delivers a press conference following a Special Meeting of the European Council at the EU Council building in Brussels on April 29, 2017

The EU's top officials will seek a meeting with Turkish President Recep Tayyip Erdogan at a NATO summit next month amid mounting tensions with Ankara, German Chancellor Angela Merkel said Saturday.

EU President Donald Tusk made the announcement to 27 European Union leaders holding a special meeting -- without Britain -- on Brexit, Merkel told reporters.

She said Tusk "told us today that he was going to ask for a meeting with President Erdogan, along with European Commission President Jean-Claude Juncker, during the NATO summit" in Brussels on May 25.

"Mr Tusk indicated he was going to consult us about this subject beforehand, which I welcome," the German leader said.

Erdogan, whose country is a key NATO member bordering the Middle East, is due to attend the 28-nation NATO summit, which is also set to welcome US President Donald Trump for the first time.

Merkel told the German parliament on Thursday that both German-Turkish and European-Turkish ties had been "severely hit" in the last few weeks as Erdogan continued his crackdown after a failed coup attempt last July.

Merkel highlighted Ankara's arrest and treatment of German newspaper correspondent Deniz Yucel, saying it was "incompatible with a constitutional state".

Merkel also voiced concerns that the April 16 referendum on expanding Erdogan's powers was not held under fair conditions.