The UN High Commissioner for Refugees (UNHCR) says at least 700 people are feared dead after a ship smuggling migrants capsized in the Mediterranean Sea.

UNHCR spokeswoman Carlotta Sami said on Sunday that only 28 people survived the incident, which took place on April 16.

According to survivors, the fishing boat had been carrying more than 700 people. The survivors were rescued after a helicopter saw them floating in the sea.

However, the Maltese navy put the presumed death toll at 650.

“We have deployed our assets along with others from Italy and we are assisting in the rescue operation,” a Maltese navy spokesman said.

The boat capsized about 60 miles off the Libyan coast and 120 miles south of the Italian island of Lampedusa. It was reportedly on its way to Europe when it capsized off Libya.

If the deaths are confirmed, the incident will be the deadliest disaster in a growing wave of drowning immigrants on their way to Europe.

In recent days, two other shipwrecks left about 450 people dead.

Reports indicate that nearly 11,000 people trying to reach Italy have been rescued since April 10.

A total of about 1,500 people seeking entry to Europe have lost their lives at sea between Libya and Italy so far this year.