Europe’s top human rights watchdog has called on Athens to end pushbacks of asylum-seekers on its borders, a practice that Greece denies carrying out.

In a letter to Greek ministers published on Wednesday, the Council of Europe’s Human Rights Commissioner said there had been “numerous credible allegations” since at least 2017 of asylum-seekers left adrift at sea or illegally returned to Turkey and that Greece had simply dismissed them.

UNHCR, the United Nations’ refugee agency, has also collected data pointing to several dozen pushbacks since January 2020, said the letter from Commissioner Dunja Mijatovic.

“I urge you (Greece) to put an end to these practices and to ensure that independent and effective investigations are carried out into all allegations of pushbacks and of ill-treatment by members of security forces,” Mijatovic said.

In a response also published by Mijatovic’s office, Athens said it had probed the allegations and found them “largely unsubstantiated”.

Greek ministers were quoted as saying in their response to the Council that “the actions taken by the Greek authorities, at our sea borders, are being carried out in full compliance with the country’s international obligations.”

They said Athens had rescued thousands of people since the beginning of Europe’s migrant crisis in 2015 and officers had to do their job “against the backdrop of an unfavorable environment of intended misleading information emanating in most cases from the smugglers’ networks”.