Malta's former leader is stepping down following an investigation into the 2017 murder of journalist Daphne Caruana Galizia.

Calls for Joseph Muscat to step down grew after a probe into the 2017 car bomb killing of anti-corruption journalist Daphne Caruana Galizia led to charges on Saturday against a prominent businessman with alleged ties to government ministers and senior officials.

The probe into the murder of Daphne Caruana Galizia, a campaigning journalist who investigated and exposed corruption, has spawned a political crisis for the government of Prime Minister Joseph Muscat.

Late journalist Caruana Galizia's family demanded Muscat's resignation on Friday.

Authorities said the migrants hijacked the tanker after it rescued them in the Mediterranean Sea, then forced the crew to head toward Europe.

Italian Interior Minister Matteo Salvini said the merchant ship, El Hiblu 1, rescued migrants in the Mediterranean Sea earlier Wednesday.

More than 1,000 people have drowned this year attempting to cross the Mediterranean Sea, while 200 hundred of those have died in the past three days, according to the International Organization for Migration.

The migrant rescue boat ended a gruelling voyage which has made it a symbol of Europe's failure to agree on immigration.

Italy and Malta have both refused to let the rescue ship with 629 people aboard dock in their ports, leaving the migrants at sea for days.

The accident happened in Zurrieq, a popular tourist destination just outside the capital Valletta that is famous for its ruins and "blue grotto."