Two women were found dead and 290 migrants rescued from two boats off the coast of Libya on Sunday, the navy said.
The migrants were rescued off the coast of Garabulli, 50 kilometres (30 miles) east of Tripoli, then taken to the capital, naval officer Meftah al-Zlitni said.
He did not give further details on how the women had died.
They had left Libya Saturday evening on a makeshift craft with 140 other migrants from various African countries, but their motor broke down a few hours later.
"We stayed put from six o'clock in the morning" until the navy arrived, said Baba Koni, a Malian who was on board the boat.
He said the motor had become waterlogged and cut out.
Zlitni said 150 migrants were on a second boat that had been about to sink when the patrol arrived.
Since the 2011 fall and killing of longtime dictator Moamer Kadhafi, Libya has become a key launch pad for migrants making desperate bids to reach Europe, often on unseaworthy vessels.
Last year, 3,116 people died attempting the crossing, according to the International Organization for Migration.
That has continued into the new year, with at least 25 people drowning on Saturday off Libya's coast in the sinking of a boat carrying as many as 150 migrants, rescue groups said.
There was however a sharp drop in arrivals in Italy during in the second half of 2017 following efforts by Rome to discourage migrants from attempting the crossing.
Some 119,000 embarked on the perilous journey, a decrease of one third on the previous year, according to Italy's interior ministry.
The first six days of 2018 saw 400 people rescued and taken to Italy, compared to 729 over the same period in 2017, it said.