Six months after a high-profile shipwreck tragedy in Greece, two leading international human rights groups have accused Athens of failing to properly investigate the circumstances around the migrant boat sinking that killed hundreds.

Amnesty International and Human Rights Watch published a damning joint report on Thursday (December 14) that said there had been "little meaningful progress" made in the investigations into whether the Greek authorities mishandled the rescue operation, as some survivors have alleged.

Example of Greece's 'abdication of responsibility'

Up to 750 people were believed to have been crammed onto the Adriana, a rusty fishing trawler that sank on June 14 southwest of the Greek mainland near the town of Pylos while attempting to travel from Libya to Italy.

Only 104 people were rescued from the ill-fated trawler, migrants mostly from Syria, Pakistan and Egypt, while another 82 bodies have been recovered to date.

"The Pylos shipwreck appears to be another tragic example of Greek authorities' abdication of responsibility for saving lives at sea," said Judith Sunderland, associate Europe and Central Asia director at Human Rights Watch.

"A full accounting of what happened is paramount to securing truth and justice for survivors and families of the victims and to help avoid future deaths."

Also read: 'My tears won’t stop falling': Families worry after deadly Greece shipwreck

Amnesty International and Human Rights Watch interviewed 21 survivors, 5 relatives of 5 people still missing, and representatives of the Hellenic Coast Guard, the Greek police, nongovernmental organizations, United Nations and international agencies and organizations.

They found that in the 15 hours between receiving the first alert that the Adriana was in their search and rescue region, and when it capsized, Greek authorities failed to mobilize appropriate resources for a rescue.

The authorities were clearly aware of indicators of distress, such as overcrowding and insufficient food and water, on the Adriana and, survivors said, knew about corpses on board and requests for rescue.

Survivors 'pleaded repeatedly for rescue'

Survivors' testimonies also challenge the authorities' claim that people on the Adriana did not want to be rescued, which in any event would not have relieved the Hellenic Coast Guard of its obligation to take all measures necessary to ensure safety at sea. Survivors consistently said they pleaded repeatedly for rescue, including to the Coast Guard itself.

Survivors said that a Coast Guard patrol boat attached a rope to the Adriana and pulled, causing the boat to capsize. They also alleged that, after the boat capsized, the Coast Guard boat was slow to activate rescue operations, failed to maximize the number of people rescued, and engaged in dangerous maneuvers.

Also read: Greece migrant boat disaster: Was the coast guard to blame?

No immediate reaction from Greek authorities

"Almost 10 years since the deadly Farmakonisi shipwreck, the Greek authorities' response to the Pylos tragedy is a crucial test of their willingness to investigate human rights violations against racialized people at the country's border," said Adriana Tidona, a migration researcher at Amnesty International.

She added: "Greece must ensure that survivors and families of the hundreds who lost their lives can safely and effectively participate in proceedings to the highest degree possible and ensure that investigations are carried out in a timely manner, guaranteeing the completeness and integrity of evidence admitted."

The allegations from survivors prompted an independent investigation last month by Greece's state ombudsman. It said the coast guard failed to conduct its own disciplinary investigation into the agency's response on June 14. In September, 40 survivors initiated legal action against Greek authorities.

It remains to be seen whether Greek authorities will respond to Thursday's report. There was no immediate reaction, but government officials have always stated that criticism of the coast guard is unfair and maintain that blame should fall squarely on smugglers who pack migrants onto unseaworthy vessels.

Also read: Shipwreck survivors pressured to accuse migrants of smuggling