More than 600 migrants hoping to reach Europe from Libya have been stopped since Friday, the navy said.
Three groups of illegal migrants were intercepted at sea on Friday and Saturday by Libya's coastguard and units in charge of securing ports, the navy said in a statement, released overnight Saturday to Sunday.
Agence France Presse quoted it as saying that the 638 people were mostly citizens from sub-Saharan African nations trying to reach Europe, and they were brought to a naval base in the capital Tripoli ahead of handing them over to an anti-immigration squad run by the interior ministry.
The navy said a first group of 334 migrants, who were on board four inflatable boats, were "rescued" on Friday.
Two other groups, of 132 and 172 people, were assisted separately on Friday and Saturday.
According to the AFP, the navy did not say if the boats were sinking or had technical problems.
Libya is a major route for migrants trying to reach Europe via the Mediterranean.