More than 200 migrants are missing after two motorboats they were travelling on sank in the Mediterranean Sea, the UN's refugee agency says, according to BBC News.

"Nine were saved after four days at sea. The other 203 were swallowed by the waves," UNHCR's spokeswoman in Italy, Carlotta Sami, said on Twitter.

She called the situation a "horrible and enormous tragedy".

The International Organization for Migration says the two boats departed from the Libyan coast last week.