"We will rescue them as there is no response from the Turkish authorities to our calls to take them back," a source in the ministry of citizen's police protection told AFP.

A video sent to media, allegedly from the Evros River region, said the group of about 80 were Yazidis, a mostly Iraq-based Kurdish-speaking religious minority.

A man speaking Kurdish on the video said the group had been stuck on one of the river islets for about six days and that several of its members required medical assistance.

Thousands of migrants, mainly from Syria, Afghanistan and Pakistan, have in recent years crossed into Greece from Turkey in the hope of making it to western Europe.

With the stepping up of patrols in the Aegean Sea making it harder for migrants to reach Greek islands, more are taking their chances by crossing the river, Greece's natural border with Turkey, and having traffickers take them from there by road.

Greece is currently under a caretaker government ahead of June 25 national elections.

The office of interim prime minister Ioannis Sarmas, a senior judge, earlier Sunday noted that it had appealed to the Turkish government "to coordinate with border authorities and prevent illegal crossings."

"In recent days, the low water level of the river Evros favours the illegal crossing of migrants, using islets that constitute both Greek and Turkish territory," the interim prime minister's statement said.

"On such an islet, about eighty immigrants ended up in the Greek section," it added.

Another group of nearly 140 asylum seekers were intercepted inside Greek territory on Thursday after crossing the river.

The previous conservative Greek government, which looks likely to return to power on June 25, has decided to extend by 35 kilometres (22 miles) a five-metre high steel fence which runs along the river.

The fence is currently 38 kilometres long, and Athens aims to carry out the extension within a year, adding a total of 100 kilometres by 2026.

burs-jph/cw