It said in a statement that the migrants hail from different nations and that those who illegally entered Libya would be handed over to their home countries.
The statement did not provide further details.
The coast guard posted images on Facebook showing a large, overcrowded vessel with most of those on board appearing to be young people.
It was one of the largest interceptions in recent months of migrants sailing to Europe, a destination for thousands fleeing conflict and poverty in the Middle East and Africa.
In August last year, Italian military vessels aided a boat crammed with 539 migrants off the southern island of Lampedusa. The boat was launched from Libyan shores.
Libya has in recent years emerged as the dominant transit point for migrants seeking a better quality of life in Europe. The oil-rich country plunged into chaos following a NATO-backed uprising that toppled and killed longtime autocrat Moammar Gadhafi in 2011.
Human traffickers in recent years have benefited from the chaos in Libya, smuggling in migrants across the country’s lengthy borders with six nations. The migrants are then packed into ill-equipped rubber boats and other vessels and set off on risky sea voyages. Officials didn’t say what kind of vessel was found over the weekend.
The International Organization for Migration has reported 1,522 dead or missing migrants in the Mediterranean this year. Overall, the IOM says 24,871 migrants have died or gone missing in the Mediterranean since 2014, with the real number believed to be even higher given the number of shipwrecks that never get reported.
