Athens, June 17 : Some 500 people still remain missing after a fishing boat carrying hundreds of migrants capsized off the coast of Greece on June 14, according to UN agencies. A joint statement issued on Friday by the International Organization for Migration (IOM) and UN Refugee Agency (UNHCR) said that while the number of people onboard the boat is not clear, it is believed to have been somewhere between 400 and 750. So far 104 people have been rescued and 78 bodies retrieved, while hundreds remain missing, and feared dead in the latest tragedy in the Mediterranean deemed to be the worst in recent years, the UN agencies said. The boat was reportedly in distress since the morning of June 13. A large-scale search and rescue operation was announced by the Greek Hellenic Coast Guard on the morning of June 14, after the boat capsized. The duty to rescue people in distress at sea without delay is a fundamental rule of international maritime law. Both shipmasters and states have an obligation to render assistance to those in distress at sea regardless of their nationality, status or the circumstances in which they are found, including on unseaworthy vessels, and irrespective of the intentions of those onboard, according to the agencies. Both the UNHCR and IOM have been on the ground in Kalamata, in southern Greece in close coordination with the authorities providing support and assistance to the survivors, including non-food items, hygiene kits, interpretation services and counselling for survivors who are traumatized following the ordeal. "It is clear, that the current approach to the Mediterranean is unworkable. Year after year, it continues to be the most dangerous migration route in the world, with the highest fatality rate. States need to come together and address the gaps in proactive search and rescue, quick disembarkation, and safe regular pathways. These collective efforts should have the human rights of migrants and saving lives at the centre of any response" Federico Soda, IOM Director for the Department of Emergencies, was quoted as saying in the statement. "The EU must put safety and solidarity at the heart of its action in the Mediterranean. In view of the increased movements of refugees and migrants in the Mediterranean, collective efforts, including greater coordination between all Mediterranean States, solidarity and responsibility-sharing, as reflected in the EU's Pact on Migration and Asylum are essential to save lives. This includes the establishment of an agreed regional disembarkation and redistribution mechanism for people who arrive by sea, which we continue to advocate for." said Gillian Triggs, the UNHCR Assistant High Commissioner for Protection. Meanwhile, the Greek caretaker Prime Minister, Ioannis Sarmas, said that a "thorough investigation of the real facts and technical judgements" would take place to determine what had caused the boat to capsize. Greece is one of the main routes into the European Union for refugees and migrants from the Middle East, Asia and Africa. Last month, the Greek government came under international criticism over video reportedly showed the forceful expulsion of migrants who were set adrift at sea. /IANS