Turkey summoned a senior German diplomat on Monday, a day after a rally in Cologne in support of the Turkish president who was not permitted to address the crowd by video link.

Turkish officials were also to meet with the top US military commander in the first direct talks since a failed coup on July 15, with Washington under pressure from Ankara to extradite the alleged mastermind, Islamic preacher Fethullah Gulen.

The coup aimed to unseat President Recep Tayyip Erdogan who has since launched a sweeping nationwide purge of suspected Gulen supporters, dismissing tens of thousands from their jobs and detaining almost 19,000 people.

The crackdown has sparked international alarm, with Prime Minister Binali Yildirim admitting there may have been some unfair treatment in the dismissals.

"There must definitely be some among them who were subjected to unfair procedures," he said in comments published by state-run Anadolu news agency on Monday.

"We will make a distinction between those who are guilty and those who are not."

- German rally -

In Germany, home to Turkey's largest diaspora, tens of thousands of Erdogan supporters rallied in Cologne on Sunday to demonstrate their opposition to the coup in an event held under tight security.

Hours before the demonstration, Germany's constitutional court rejected an application to show via video link live speeches from Turkey by politicians including Erdogan, over fears they could work up the crowd.

The decision sparked anger in Turkey, with presidential spokesman Ibrahim Kalin calling the move unacceptable and a "violation of the freedom of expression and the right to free assembly".

A spokeswoman for the German embassy told AFP that the charge d'affaires had "been summoned to the Turkish foreign ministry at 1:00 pm (1000 GMT)" on Monday over the rally.

But Berlin played down the incident, saying such "invitations" were nothing out of the ordinary.

"In the day-to-day dealings between countries, it is a daily event -- normal for a representative of a country to be called in to the foreign ministry of his host country," German foreign ministry spokesman Martin Schaefer told journalists.

The tension comes as ties between Germany and Turkey were already strained over the German parliament's decision to brand as genocide the World War I-era Armenian massacre by Ottoman forces.

- Tensions with Washington -

Also on Monday, General Joseph Dunford, chairman of the US joint chiefs of staff, was to meet with Yildirim and Turkish chief of staff General Hulusi Akar.

Tensions between the two NATO allies have been aggravated by the foiled putsch, with some Turkish officials even alleging that Washington could have had a hand in the plot. The suggestion has been firmly denied by top US officials.

Turkey is now requesting the extradition of Gulen -- who has lived in self-imposed exile since 1999 -- from his leafy compound in Pennsylvania.

"We do not want (the US) to be in a position that will make us question our friendship," Yildirim said.

"If they keep on dragging (their) feet on the Gulen issue... then things will take a different course, because events of July 15 are crystal clear."

After a cabinet meeting in Ankara, Deputy Prime Minister Numan Kurtulmus told reporters that Washington would have to chose between support for a "terrorist chief" and the citizens of Turkey.

Last week, Erdogan lashed out at the top US general in the Middle East, General Joseph Votel, after he expressed concerns about the future of military relations between the two allies in the wake of the putsch.

Meanwhile Turkey on Monday said it had arrested 11 fugitive soldiers suspected of involvement in an attack on Erdogan's hotel during the night of the coup, Kurtulmus said.

Erdogan was staying in the western seaside resort of Marmaris on July 15 but dashed to Istanbul just before the hotel came under attack from rebel soldiers determined to oust him from power.

Just one soldier from the attack group now remains at large, Kurtulmus added.