"Human life and human freedom are not, and should not be, pawns to power games and blackmail," Tsipras said in a statement to Documento newspaper.

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.

Greece had hoped to secure their release before Sunday's Orthodox Easter celebration.

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

But Athens contends that Turkish authorities have not given adequate details of the charges and on what evidence they are based.

According to Turkey's state-run Anadolu news agency, the soldiers have been charged with "attempted military espionage" as well as entering a forbidden military zone.

The issue has strained an already tense relationship between the two NATO allies and regional rivals.

Turkish President Recep Tayyip Erdogan and members of his government have escalated attacks on Greece after its failure to extradite eight Turkish soldiers that Ankara said were part of an attempted 2016 coup.

The Greek Supreme Court has conclusively blocked the extradition of the eight Turkish soldiers, arguing that they would not have a fair trial in their home country amid an ongoing purge of suspected Erdogan opponents.

Additionally, Ankara and Athens are at loggerheads over the exploration of gas reserves in the eastern Mediterranean.

Tsipras earlier this week called on the Turkish judiciary to "speed up" its processing of the case.

"In the past, we returned Turkish soldiers who crossed a few metres into Greece whilst on patrol. I expect the Turkish president to do the same," he said.