Turkey is holding in pre-trial detention two Greek soldiers who crossed the border on March 2, claiming to have lost their way in the fog.

The pair, held in the northern Turkish province of Edirne, have been charged with espionage.

"They (Greece) ask us to give back the Greek soldiers and we told them 'if you make such a demand, you should first give us FETO soldiers involved in a coup against our state'," Erdogan told the private NTV television in an interview.

FETO is a name Ankara gives for a movement led by Muslim preacher Fethullah Gulen who it blames for masterminding the failed coup aimed at unseating Erdogan.

Gulen, based in the US state of Pennyslvania, has denies the accusations.

"If they are handed to us, we will consider" the situation on Greek soldiers, he said.

Greek Prime Minister Alexis Tsipras earlier this month demanded the release of the two soldiers, arguing that they should not be "pawns to blackmail".

Turkey's ties with Greece have taken a strained turn over Athens' failure to extradite eight Turkish soldiers Ankara says were part of the coup bid. Greek authorities say they would not have a fair trial in their home country as the purge of Erdogan opponents continue under the state of emergency.

Erdogan on Saturday said Greece had become a "first stop" for coup suspects who later flee to other European countries.