The Greek coastguard is responsible for the deaths of dozens of migrants crossing the Mediterranean who were forced to turn back or in some cases were deliberately thrown overboard, an investigation has found.

More than 40 people traversing the Mediterranean on small boats are said to have died due to the Greek coastguard's activities, which included forcing punctured vessels to go back out to sea.

Nine of those people are believed to have died after they were deliberately pushed into the water by coastguard officers, according to eyewitnesses from NGOs, local media and the Turkish coastguard, which often receive migrants turned away by Greece.

It comes just days after hundreds of demonstrators gathered in Athens on Friday to mark the first anniversary of a shipwreck that killed hundreds more migrants off Greece, demanding answers about the causes of the disaster and the fate of relatives.

Up to 700 migrants from Pakistan, Syria, and Egypt were crammed into the fishing trawler 'Adriana' bound for Italy from Libya that capsized off southwestern Greece on June 14 last year, even though the Greek coast guard had been monitoring it for hours.

Some 104 people were rescued, but only 82 bodies were recovered. 

The catastrophe, one of the worst Mediterranean boat disasters on record, raised searching questions about how the European Union is trying to stem flows of migrants - and the actions of Greece's coastguard. 

The investigation, published this week by the BBC, found at least 40 migrants died due to the actions of the Greek coastguard in 15 incidents across three years between May 2020 - 2023.

It spoke with several migrants who suffered maltreatment at the hands of coastguard officers and police, as well as others who witnessed the deaths of fellow migrants who were thrown into the water even after having reached land.

A Cameroonian man who reached Greece told BBC investigators how a man from the Ivory Coast drowned in front of him after being thrown back into the sea.

'We had barely docked, and the police came from behind. There were two policemen dressed in black, and three others in civilian clothes. They were masked, you could only see their eyes.'

'They started with the [other] Cameroonian. They threw him in the water. The Ivorian man said: ''Save me, I don't want to die…''

'Then eventually only his hand was above water, and his body was below. Slowly his hand slipped under, and the water engulfed him.'

A Somali migrant claimed Greek officers zip-tied his hands before shoving him into the water off the back of a boat, while a man from Syria shared how several children drowned after the coastguard left them near Turkey in damaged rafts.

'We immediately began to sink, they saw that… They heard us all screaming, and yet they still left us,' he told the BBC.

'By the morning seven or eight children had died.'