Seven people have been rescued and 21 others remain missing at sea after the boat they were travelling in capsized off the island of Lampedusa, the Italian coast guard has said.

The survivors, all Syrian nationals, were picked up from a semi-sunken boat about 10 nautical miles (18.5 kilometres) southwest of Lampedusa, a statement said on Wednesday.

Chiara Cardoletti, head of the United Nations High Commissioner for Refugees (UNHCR) in Italy, wrote on X that the survivors were in “critical” condition and had lost relatives at sea.

The survivors told rescuers they had set off on Sunday from Libya, and that 21 of the 28 people they had aboard, including three children, had fallen into the sea during rough weather.

The boat “capsized repeatedly, leaving people clinging to the side of the boat as their family members drowned around them,” Nicola Dell’Arciprete, country coordinator for Italy for the UN Children’s Fund (UNICEF), said in a statement.

The Italian office of the UN refugee agency told the Reuters news agency that Sudanese people were also on the boat, which is believed to have departed from the port of Sabratha, west of Tripoli.

The coast guard said it had taken the survivors to Lampedusa and had deployed naval and air units to look for the missing people.

The central Mediterranean is among the world’s deadliest migration routes.

According to the International Organization for Migration, more than 2,500 migrants died or went missing attempting the crossing last year, and 1,047 this year, as of Tuesday.

The most recent figures from the Italian Ministry of the Interior recorded that more than 43,000 migrants had reached Italy so far in 2024, well down from previous years.