A Syrian migrant who says he was illegally pushed back to Turkey by Greek authorities has sued the European Union border agency Frontex for alleged complicity.

The association mounting his legal case told Agence France-Presse (AFP) on Thursday that the lawsuit was lodged on March 10, according to the European Court of Justice's website.

The plaintiff, Alaa Hamoudi, is seeking 500,000 euros ($550,000) from Frontex over action he says the Greek coast guard took on April 28-29, 2020, according to the Front-Lex legal association representing him.

Front-Lex said after Hamoudi arrived on the Greek island of Samos with around 20 other asylum-seekers, they were loaded by Greek authorities onto a crowded inflatable dinghy and abandoned at sea for 17 hours.

A Frontex plane surveilled the situation at the time, alleged Hamoudi, who now resides in Turkey.

Such an act, if proven, could constitute "refoulement" – the forcible return of refugees or asylum-seekers, which is illegal under international law binding on all countries.

Frontex, the EU's biggest agency with a budget of 750 million euros this year, has been helping the Greek coast guard monitor the Greek side of the maritime border with Turkey.

An October 2020 investigation carried out by the open-source analysis group Bellingcat with the journalist cooperative Lighthouse Reports and several media outlets, including Der Spiegel, determined that Frontex was complicit in refoulement in Greek waters.

The findings triggered several inquiries in the EU over Frontex and its practices.

However, a working group set up by Frontex's own management board released a conclusion that there were "no indications" of the April 28-29 incident reported by those outlets.

The European Anti-Fraud Office (OLAF) in February sent conclusions from its own investigations to Frontex's board, but those have so far been kept under a cloak of confidentiality.

Meanwhile, the Human Rights and Equality Institution of Turkey is preparing a report examining the human rights violations of Greece in the Aegean Sea.

Accordingly, the number of irregular migrants pushed back in the Aegean in the last three months has reached 3,185.

Turkey and Greece have been key transit points for migrants aiming to cross into Europe, fleeing war and persecution to start new lives. The journey of hope of irregular migrants either ends in the blue waters of the Aegean or turns into a nightmare due to the inhumane practices of Greek coast guard units. In recent years, hundreds of thousands of asylum-seekers have made the short but perilous journey across the Aegean to reach Northern and Western Europe in search of a better life. Hundreds of people have died at sea as many boats carrying refugees often sink or capsize. The Turkish Coast Guard Command has rescued thousands of others.

Turkey and many international human rights groups have accused Greece of large-scale pushbacks and summary deportations without migrants being given access to asylum procedures, saying it violates humanitarian values and international law by endangering the lives of vulnerable migrants, including women and children. They also accuse the European Union of turning a blind eye to this blatant abuse of human rights.

Greece’s pushbacks of irregular migrants increased by 97% in 2021 compared to the previous year, according to a report by the Norwegian nongovernmental organization (NGO) Aegean Boat Report, which monitors the movement of migrants in the area.

Most recently, 19 irregular migrants were found frozen to death near the Greek-Turkish border after Greek border officials stripped them off their clothes, stole their valuable possessions and pushed them back into Turkish territory.

Interior Minister Süleyman Soylu shared several photos of the sites where the migrants were found, with the victims' lifeless bodies blurred.

Commenting on the incident, President Recep Tayyip Erdoğan slammed the EU's border protection agency Frontex for cooperating with Greece and the bloc for turning a blind eye to the deaths of migrants.

Defense Minister Hulusi Akar also said: "In the last three years, they (Greece) pushed 85,000 refugees ruthlessly, criminally and inhumanly, especially at sea. There has to be another way. This must be stopped immediately."

Turkey's coast guard says it has rescued more than 15,000 migrants pushed back by Greece last year.

Athens denies violating international conventions and insists it is doing its duty to protect the EU's southeastern borders against illegal crossings. The EU has infuriated Turkey by largely supporting the Greek position. EU's Frontex has also been involved in some Greek pushbacks of migrants.