The Libyan coastguard intercepted about 550 migrants from sub-Saharan Africa on Tuesday after they set out to cross the Mediterranean in four rubber boats, Tripoli coastguard spokesman Ayoub Qassem said.
The migrants from various African countries, including 30 women and three children, were stopped off the Libyan coast near Sabratha, a city 80 km west of the capital Tripoli.
Another 850 migrants were intercepted in the same area on Sunday.
Libya is a frequent departure point for migrants hoping to cross the Mediterranean to Europe and the number attempting the journey is expected to rise with calmer weather during the summer.
Migration flows from Libya increased sharply in 2014 and 2015 and has been slightly lower so far this year, according to Italian data.
Migrants stopped by the coastguard close to the shore are sent back to overcrowded detention centres in Libya. Those who make it further out to sea are often picked up by international rescue missions and brought to European ports.
The International Organisation for Migration (IOM) said on Tuesday that some 2 725 migrants were rescued by various vessels attempting to reach Europe from Libya over the past 24 hours.
The number of migrants who have died trying to cross the Mediterranean so far this year is 1 370, a drop of nearly 25% compared with the same period last year, the IOM said.