Rescue workers were searching the surrounding area for any other possible victims, the army's deputy commander Colonel Edric Zahra told a press conference.

"The boat capsized suddenly while the rescue operation was underway," he said.

An armed forces (AFM) patrol boat had approached the migrant vessel after it was spotted off Malta's southern coast earlier on Friday.

"These migrant boats are usually heavily loaded with people. The chances are that when people move about, the boat loses balance," Zahra said.

"The migrants ended up in the water," he said.

"Eight are receiving medical care in hospital and unfortunately five were brought ashore dead."

He said the dead were four men and a woman.

The migrants are believed to have set sail from Libya but hail from Egypt, Eritrea, Ghana and Syria.