A Turkish court ruled on Wednesday to keep a US consulate employee in jail as his trial on espionage charges continues.

Metin Topuz, a Turkish citizen and liaison for the US Drug Enforcement Administration who has been jailed since 2017 told a judge no credible evidence had been submitted against him.

The case has added to growing tension between Ankara and Washington, who have also been at odds over developments in Syria and Turkey's purchase of Russian missile defence systems.

Turkish authorities accuse Mr Topuz of ties to US-based Muslim preacher Fethullah Gulen, who Ankara says ordered an attempted coup the year before.

His next court appearance was set for March 10.

"The charges are based on unrealistic allegations and contradictory testimonies of so-called witnesses," Mr Topuz told the Istanbul court.

"Not one single piece of evidence has been presented to the court that would convince a rational person that I tried to destroy the Turkish republic," he said, referring to claims made by the prosecution.

The trial has been delayed as prosecutors try to locate a witness who Topuz's lawyers say has fled to Italy and has no bearing on the case.

Since the failed 2016 coup, tens of thousands of people have been arrested over suspected ties to Mr Gulen and more than 100,000 people have been sacked or suspended from public sector jobs. Mr Gulen rejects the coup accusations.

Washington's refusal to extradite Mr Gulen, combined with differences over the Syrian conflict and Turkey's decision to buy a Russian missile defence system, have put unprecedented strain on relations between the Nato allies.

The court has repeatedly said it wants to hear one remaining witness in the case.