At least 79 people have died and hundreds more are feared missing in the deadliest migrant shipwreck off Greece this year. The victims, nearly all of them men from Afghanistan and Pakistan, drowned when the large trawler they were travelling in capsized off the southern Peloponnese. It was unclear how many passengers were missing from the vessel, which had set out from eastern Libya and was heading for Italy. By nightfall, Greece’s caretaker government had declared three days of national mourning to mark the tragedy. “There has been a dramatic rise in the death count, which is climbing by the hour,” said one Greek official. “Speculation is rife that as many as 600 people were onboard but that has not been confirmed. The ship is under the water. It has sunk.” About 104 passengers had been rescued as of Wednesday afternoon, he said. Ioannis Zafiropoulos, the deputy mayor of the southern port city of Kalamata, where survivors were taken, said his information indicated there were more than 500 people onboard. A European rescue support charity said it believed about 750 people were onboard, and the UN’s migration agency cited an estimate of as many as 400. Coastguard vessels, a navy frigate, military transport planes, an air force helicopter and an array of private craft were participating in the search for survivors. Rescue efforts were initially hampered by strong winds. Greek media outlets quoted survivors as saying the ship went down almost instantaneously, close to the deepest area of the Mediterranean Sea. “The engine stopped and it sank in minutes,” said one. On Wednesday evening the first aerial pictures emerged of the overcrowded vessel before it capsized. The blue trawler appeared to have hundreds of people on board. “The outer part of the boat was full of people and we assume that was the case below deck too,” Nikos Alexiou, a spokesperson for the Hellenic coastguard, told reporters. “The boat was overcrowded. A precise number cannot with certainty be given but what is sure is that it is very big.” Greek authorities and officials from the EU border agency Frontex were alerted to the stricken ship late on Tuesday. Repeated calls to the vessel offering help were declined, the coastguard said in a statement. “In the afternoon, a merchant vessel approached the ship and provided it with food and supplies, while the [passengers] refused any further assistance,” the coastguard said. A second merchant ship later offered further supplies and assistance, which were turned down, the agency added. A coastguard patrol boat reached the vessel in the evening “and confirmed the presence of a large number of migrants on the deck”, the statement said. “But they refused any assistance and said they wanted to continue to Italy.” Smugglers are taking ever greater risks to evade patrols. They are increasingly operating in international seaways with the aim of dropping off their human cargo in Italy rather than heavily guarded Greece. “We are seeing growing numbers plying open seas that are more dangerous because they are prone to more stormy weather,” said Natassa Strachimi, a lawyer with Refugee Support Aegean, an NGO that provides legal aid to asylum seekers. “And the journeys are taking much longer because the destination is Italy.” The Greek migration ministry blamed international smuggling networks for putting migrants’ lives at risk, while the UN high commissioner for refugees, Filippo Grandi, called on governments to work together to create safe pathways for people fleeing poverty and war. Greece has been criticised for forcibly expelling would-be asylum seekers in violation of international law. Its former centre-right government, which is facing re-election in polls later this month, has denied the “pushbacks”, calling its migration policy “tough but fair”. A video released last month showed refugees who had reached the island of Lesbos being forcibly placed on a Greek coastguard vessel before being set adrift and picked up by the Turkish coastguard. Kyriakos Mitsotakis, the country’s prime minister until May, and the main leftwing opposition leader, Alexis Tsipras, announced they would suspend their electoral campaigns as the scale of the tragedy became apparent. The European Commission president, Ursula von der Leyen, said she was deeply saddened by the tragedy. Last week EU interior ministers agreed radical reforms on migration laws and a new pact with Tunisia to reduce migration, with specific funds intended to stem the loss of life in the Mediterranean. UN data suggests that about 72,000 refugees and migrants have arrived in Italy, Spain, Greece, Malta and Cyprus, countries bordering the Mediterranean, so far this year. Greece has long been one of the main routes for people fleeing war, persecution and poverty in the Middle East, Asia and Africa.