Libyan coastguards intercepted about 850 migrants on Sunday off the coast near the western city of Sabratha, a spokesman said.
Ayoub Qassem said the migrants were from various African countries and among them were 69 women, including 11 who were pregnant, as well as 11 children. They were travelling in inflatable rubber boats, he said.
Libya is a major departure point for mainly sub-Saharan African migrants trying to reach Europe through crossings arranged by people smugglers. Migrants are often given flimsy boats that are ill-equipped for travelling across the Mediterranean.
The flow of migrants has increased amid the turmoil that followed the 2011 uprising against long-time Libyan ruler Muammar Gaddafi.
More than 30,000 have already crossed on the central Mediterranean route to Italy this year, and more are expected to attempt the journey in calmer weather during the summer.
The International Organization for Migration has identified 235,000 migrants in Libya, but says the real number is likely to be much higher, between 700,000 and one million.
Some of these stay in Libya to work before either returning home or trying to continue on towards Europe.