At least 78 migrants died after their fishing boat sank off the Peloponnese, Greece’s coastguard said Wednesday, as fears mounted that the death toll could rise much higher. Some 100 people were rescued after the boat capsized in international waters in the Ionian Sea in an operation complicated by strong winds, the coastguard said. A migration ministry source told AFP that according to the coastguard there could have been “hundreds” of people on the fishing boat. “We fear there will be a very large number of missing persons,” the official said. The International Organization for Migration (IOM) acknowledged fears of a large number of missing people, noting in a tweet: “We fear more lives were lost. Initial reports suggest up to 400 people were onboard.” Greece’s head of state, President Katerina Sakellaropoulou, said she would visit the port of Kalamata later Wednesday to confer with senior officials on the rescue and accommodation response. The worst migrant tragedy in Greece was in June 2016 when at least 320 people were listed as dead or missing, according to AFP records going back to 1993. The IOM until Wednesday had listed 48 migrants missing in the eastern Mediterranean so far this year, compared to 378 a year earlier. Along with navy vessels, the rescue operation included an army plane and helicopter as well as six other boats that were in the area. “Since very early Wednesday, an extensive rescue operation is underway off Pylos, after a fishing boat capsized with a large number of migrants onboard,” the coastguard said. Greek media reported that nearly 30 people have been taken to the port’s hospital, though the coastguard limited the number to just four. The coastguard said a surveillance plane with Europe’s Frontex agency had spotted the boat on Tuesday afternoon, but the passengers had “refused any help”.