The sinking killed more than 30, most of them women and children, when the boat packed with people desperate to reach European shores went down off Malta near the Italian island of Lampedusa, according to officials.
It came just over a week after a similar tragedy killed more than 300 Africans in the deadliest refugee disaster to date in the region, prompting the European Union to call for sea patrols to cope with the flood of migrants knocking on its doors.
Thirty-three people, including infants and children, are known to have died as a result, according to a Maltese military source. Some 143 people have so far been rescued, an AFP correspondent said.
The Maltese navy dispatched rescue ships and helicopters and diverted commercial vessels to the area, while Italy sent two naval vessels and helicopters carrying inflatable life rafts.
European Union Commissioner for Home Affairs Cecilia Malmstroem said she was following the rescue operations "with sadness and anxiety" and praised Italy and Malta for their swift response.
The Commission has been urging EU states to pledge planes, ships and funds for EU border guard service Frontex, whose budget has been cut.
Italian Prime Minister Enrico Letta called the latest tragedy "a new and dramatic confirmation of the state of emergency".
"Italy and Malta cannot be left all alone, this is a European problem," said his Maltese counterpart, Joseph Muscat, who spoke with Letta by phone.
The boat, bound for Lampedusa, capsized after those aboard attempted to catch the attention of a military aircraft flying overhead by gathering at one end of the vessel, the Maltese navy said.
