The UN refugee agency has voiced alarm at increasing reports of “horrific incidents” where asylum-seekers and migrants trying to slip into Greece and other European countries are allegedly being forced back.

Athens denied the claims, and said the UNHCR appeared to have fallen for propaganda from neighbouring Turkey, from which thousands of asylum seekers from other countries enter Greece every year.

Relations between the historic regional rivals are frosty due to a series of disputes, including over migration.

UN High Commissioner for Refugees Filippo Grandi decried “the increasing number of incidents of violence and serious human rights violations against refugees and migrants at various European borders”, with several resulting in loss of life.

Greece was the one country he mentioned by name.

“We are alarmed by recurrent and consistent reports coming from Greece’s land and sea borders with Turkey, where UNHCR has recorded almost 540 reported incidents of informal returns by Greece since the beginning of 2020,” Mr Grandi said.

He added that three people have reportedly died since September 2021 in the Aegean Sea after being allegedly forced back from Greek waters.

In some cases, Mr Grandi said, migrants were reportedly “left adrift in life rafts or sometimes even forced directly into the water, showing a callous lack of regard for human life”.

He added: “Equally horrific practices are frequently reported at land borders, with consistent testimonies of people being stripped and brutally pushed back in harsh weather conditions.”

About a million people entered Greece through Turkey in 2015, on their way to seek a better life in Europe’s prosperous heartland.

Greek authorities, assisted by EU partners, subsequently tightened border controls and built a fence along the land frontier with Turkey, drastically limiting arrivals.

However, allegations of illegal returns of migrants by Greece to Turkey – by land and sea – have increased.

On February 3, Turkey said 19 migrants were found frozen to death on its land border with Greece, and accused Greek authorities of taking away their clothes and shoes and forcing them back into Turkey.

Athens has rejected the Turkish claims – as well as others of pushbacks at sea – as untrue.

In turn, it accused Turkey’s coast guard of escorting boats full of asylum seekers to Greek waters and harassing Greek coast guard vessels.

Matters came to a head two years ago, when Turkey declared its land borders with Greece open to migrants.

Days of clashes ensued between Greek border forces and thousands of people trying to push into Greece.

On Monday, Greek migration minister Notis Mitarachi said he was “surprised” at Mr Grandi’s statement.

“Greece protects the external borders of the European Union, in total compliance with international law and in full respect of the charter of fundamental rights,” he said.

“It is deeply troubling that Turkish-driven propaganda and fake news about illegal migration is so often mistakenly taken as fact.”

Mr Mitarachi also accused Ankara of ignoring a 2016 deal with the EU designed to slow illegal migration from Turkey to Greece.

“In the last seven years alone, Greece has provided safe harbour for over one million people,” he said.