Around 700 people are thought to have died after a fishing boat of migrants capsized in the Mediterranean Sea.
Reuters reported that the 20m-long vessel was reportedly carrying more than 700 migrant when it sank 70 miles from the Libyan coast, south of the Italian island of Lampedusa.
According to Italian authorities, 28 people were rescued and 24 bodies have been recovered so far.
UNHCR spokeswoman Carlotta Sami was quoted by the news agency as saying: "The boat capsized because people moved to one side when another vessel that they hoped would rescue them approached."
Italian and foreign naval and coast guard vessels, patrol boats, merchant ships and helicopters are supporting the search-and-rescue operation, which is being coordinated by the Italian Coast Guard in Rome.
Recently, hundreds of people were reported missing after a double-deck boat carrying more than 500 people capsized about 120km south of Italy’s Lampedusa Island.
In February, around 300 people died in the Mediterranean Sea attempting to travel from Africa to Italy.
The UNHCR said some 31,500 people are known to have made irregular crossings to Italy and Greece this year, and that numbers are rising as sea and weather conditions improve.
In 2014, around 219,000 refugees and migrants crossed the Mediterranean and at least 3,500 lives were lost.
Following this latest incident, several government leaders have called for emergency talks, Reuters reported.
EU Foreign Policy Chief Federica Mogherini said foreign ministers would discuss the immigration crisis at a meeting in Luxembourg and European Council President Donald Tusk stated he is considering calling a special meeting of EU leaders.