"Many of the bodies are small toddlers," tweeted Chris Catambrone of the non-profit group MOAS, which was helping in the rescue effort.
MOAS tweeted photos showing survivors in orange life vests bobbing in Mediterranean waters as they awaited rescue.
"The immediate intervention of the coast guard boat Fiorillo and the MOAS boat Phoenix permitted the rescue of the majority of the migrants who had fallen into the water," the Italian coast guard said in a statement today evening.
The capsizing incident was one of several rescue operations coordinated by the Italian coast guard. In all, some 1,800 migrants were rescued today from unseaworthy dinghies or wooden fishing boats.
A commercial tugboat and three cargo ships in the vicinity were pressed into service to save lives, along with vessels from the Italian navy, a European patrol force and non-profit vessels, the coast guard said.