Around a million people -- mainly fleeing the war in Syria -- reached Europe's shores in 2015

Greece's top administrative court on Friday approved the forced deportation of two Syrian refugees, setting a precedent for hundreds of similar cases, a justice source said.

Over 750 Syrian exiles are likely to be affected by the ruling by the Greek council of state, a source with knowledge of the case told AFP.

The refugees, two men aged 22 and 29, had filed a legal challenge after asylum committees rejected their pleas to not be returned to Turkey, from where they entered Greece last year.

Dimitris Christopoulos, president of the International Federation for Human Rights (FIDH), said the ruling "violates the refugees' rights".

Rights groups supporting the pair can contest the ruling at the European Court of Human Rights.

The deportations are part of a pact between Turkey and the European Union that was designed to stem the flow of refugees and migrants after it reached historic proportions in 2015.

Around a million people -- mainly fleeing the war in Syria -- landed in Europe that year alone.

Deporting Syrian refugees to Turkey assumes that this fellow Muslim country is a safe haven for them.

But rights groups dispute this, arguing that there are few guarantees that Syrian refugees can find shelter and work in Turkey, while there is evidence of abuse and exploitation.

In July, a heavily-pregnant Syrian refugee was raped and bludgeoned to death by rock-wielding attackers at her home in Turkey, just days before she was due to give birth.

And her 10-month-old baby boy was strangled to death in a brutal double murder that sparked shock and outrage.

Homosexual refugees are especially at risk in Turkey. Last year, a Syrian LGBT refugee was found mutilated and decapitated in Turkey.

Transgender Europe has said Turkey has the highest rate of trans murders in Europe.