A retired Greek admiral has blamed the country's coast guard for the latest migrant boat tragedy that killed 78 people with hundreds more still missing.

Speaking to the Greek Radio and Television Corporation ERT earlier Friday, Nikos Spanos said that before it sank, Greek authorities asked the overloaded vessel if it needed help despite receiving a distress signal.

"The Greek Coast Guard teams had to intervene anyway," Spanos said, criticizing authorities' claim that the boat did not request help and rejected offers for assistance.

"The boat was a floating cemetery, a very old boat with no documentation," he said. "We do not ask the people on the boat, which is in danger of sinking, if they need help," said Spanos.

He claimed search and rescue ships that were close to the area where the incident occurred did not immediately take action.

The migrant boat sank off southwestern Greece early Wednesday. While more than 100 passengers were rescued, nearly 500 are missing in the surrounding Mediterranean waters and 78 bodies have been recovered, according to U.N. officials.