The leaders of Italy's populist coalition parties are sparring over migrants stranded at sea aboard private rescue vessels.

Aboard the Sea-Watch 3 are 32 migrants rescued on Dec. 22 from smugglers' boats launched from Libyan shores, while 17 other migrants were rescued days later by another private vessel, also in the southern Mediterranean.

The aid boats are sheltering from rough seas near Malta's coasts, where they took on a fresh crew and supplies.

Deputy Premier Luigi Di Maio, who heads the 5-Star Movement, insisted Saturday that Malta let the migrants disembark so Italy can take in 10 mothers and their children. But fellow Deputy Premier and anti-migrant League leader Matteo Salvini retorted that Italy won't take any.

Malta won't allow disembarking, contending they were rescued outside its search-and-rescue area.