A rescue operation is under way after a boat carrying an estimated 700 migrants capsized in Libyan waters, 120 miles south off Lampedusa.
Twenty-eight people have been reported rescued, while a number of bodies have been washed ashore in Libya.
The migrants reportedly fell overboard when they ran to draw the attention of a passing vessel. The boat is said to have capsized at midnight.
The disaster could become one of the worst over the decades of the migrant situation in the southern Mediterranean, which has seen the death toll rise over 1,500 since the beginning of 2015, Reuters reported.
“At the moment, we fear that this is a tragedy of really vast proportions,” Carlotta Sami, a spokeswoman for the UN High Commissioner for Refugees, told SkyTG24 television.
“The first details came from one of the survivors who spoke English and who said that at least 700 people, if not more, were on board,” Sami added.