Turkey has refused to release two Greek border guards arrested on suspicion of espionage, in a move that risks inflaming already strained ties between the two Nato members.

Lawyers had demanded that the two men – a lieutenant and sergeant – be freed on Monday, arguing they had accidentally strayed across the heavily defended frontier while on patrol. Greece’s army command says the pair got lost in bad weather.

The guards, who have since been photographed in fatigues and with their heads covered, insist they were tracing footsteps in the snow that they thought belonged to illegal immigrants when they unwittingly entered Turkey last Thursday.



But a court convening in the town of Edirne, where the two are being held in a high-security prison, said the soldiers had given contradictory testimonies. Turkey’s state-run television reported that an in-depth investigation had been requested before officials determine what charges should be brought against the pair.

Media reports said officials were scrutinising photographs allegedly taken by the Greeks on mobile phones, as well as digital equipment.

Greece’s foreign minister, Nikos Kotzias, said: “Turkey ought to apply the provisions of international law and not turn a routine procedure into a major legal and political problem.”

There are fears the soldiers were detained in a tit-for-tat move by Turkish authorities eager to secure the extradition of eight Turkish military personnel who fled to Greece after an attempted coup against Recep Tayyip Erdoğan’s government in July 2016. None of the eight have been returned to Turkey as Greek courts have ruled they would not receive a fair trial there.

The arrests come against a backdrop of rising Greek-Turkish tensions. Last month a Turkish patrol boat rammed a Greek coastguard vessel near a disputed islet in the Aegean Sea, causing extensive damage. Recently Turkey dispatched warships to stop oil and gas exploration off Cyprus.

“I am deeply concerned at what we are seeing,” Greece’s former foreign minister Dora Bakoyannis told the Guardian. “The mood in Turkey has shifted. Erdoğan is not the man he was 10 years ago. He is totally unpredictable.”

Indicative of the tensions, Erdoğan’s close adviser Yiğit Bulut said on Monday that, if challenged, Ankara would defend disputed isles in the Aegean “to the death if Erdoğan gives the order”. Greek rightwing nationalists took to the streets late on Monday to protest against Turkey’s perceived aggressiveness.

The rise in tensions has caused growing alarm internationally. “The atmosphere of overheated nationalism in the region, and certainly in Turkey, is making it very difficult to defuse tensions,” said Ian Lesser, the vice president for foreign policy at the US Germany Marshall Fund.

“There is always a risk of an accident. Greece and Turkey have had a very well-functioning détente since the late 1990s but unfortunately the mood, especially since the attempted coup, makes it very hard for Turkey to adopt a conciliatory approach in relations with its neighbours.”