Greek Prime Minister Alexis Tsipras on April 7 demanded the release of two soldiers jailed in Turkey, arguing that they should not be “pawns to blackmail.”

“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, according to Hurriyet Daily News.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 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.

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 meters into Greece whilst on patrol. I expect the Turkish president to do the same,” he said.