A migrant boat capsized between Sicily and Tunisia on Friday and hundreds of people were in the sea, the Italian navy said, and the national news agency ANSA said corpses had been spotted.
The incident occurred just over a week after at least 319 people drowned when a boat carrying Eritrean and Somali migrants sank near the southern Italian island of Lampedusa.
"There are at least 200 people in the sea and our helicopters are picking them up," said a navy spokesman, adding that two navy ships were also on the scene.
Last week's disaster was one of the worst in a long migrant crisis that has seen tens of thousands of people arriving in small, unsafe boats in southern Italy. Lampedusa, a tiny island located midway between Sicily and Tunisia, has borne the brunt.
According to the United Nations High Commissioner for Refugees, 32,000 have arrived in southern Italy and Malta this year alone, around two thirds of whom have filed requests for asylum.
Although most migrants come from sub-Saharan Africa, this year many are fleeing the Syrian civil war or political turmoil in Egypt and other parts of North Africa. Many are drawn by hopes of finding work in Europe and often do not stay in Italy.