Rescuers pulled nearly 300 people from two rubber boats in waters off the Libyan coast on Friday and were looking for 100 more believed to be on a another boat missing since Sunday.
Thousands fleeing violence or looking for better opportunities in Europe have already taken to the sea this month, braving the winter weather. Many more are expected as temperatures rise.
The U.N. refugee agency says that 247 people are known to have died or disappeared in the Mediterranean so far in January.
Rescuers from the Spanish organization Proactiva Open Arms found Friday’s boats traveling 24 miles (40 kilometers) north of Sabratha, in the Libyan cost.
Laura Lanuza, a spokeswoman with the Spanish NGO, said the 299 sub-Saharan migrants were in good health and would be transferred to a port in Sicily.