Up to 40 African migrants are believed to have drowned after their inflatable boat sank near the Libyan coast, survivors have told the United Nations refugee agency after reaching Italy.
"They said between 35 and 40 people died on Wednesday morning," Carlotta Sami, the UNHCR spokeswoman for southern Europe, said on Thursday.
All the dead came from sub-Saharan countries such as Senegal, Mali and Benin.
A team from the Save the Children charity that interviewed some of the survivors said up to seven children, aged about 15 or 16, were also believed to have died in the incident.
Sami told the Reuters news agency that the boat they were travelling in started to disintegrate shortly after it put to sea from the Tripoli area.
"Unfortunately, the rubber was of a very bad quality," she said, speaking by telephone from Sicily, where the survivors had come ashore after being rescued by a German navy vessel.
Save the Children said the German ship brought 283 refugees and migrants to Port Augusta. Two other boats brought a further 669 immigrants to Sicily and southern Italy during the day.
Italy has become one of the main entry points in Europe for immigrants seeking a better life, with more than 85,000 migrants - mostly from Africa and the Middle East - reaching the country so far this year via the Mediterranean.
However, many of the boats are not seaworthy and the United Nations estimates that some 1,900 would-be migrants have died since January trying to make the crossing.
COUNTING THE COST: Migration inside and outside Africa
An estimated 150,000 migrants have reached Europe by sea so far in 2015, most of them in Greece and Italy, the International Organization for Migration (IOM) said earlier this month.
The vast majority of the migrants fleeing war and poverty in Africa and the Middle East depart from Libya, where human traffickers have taken advantage of a breakdown in order to build up a lucrative business.
EU foreign ministers last month approved the launch of a military operation against people smugglers in the Mediterranean, with ships and aircraft conducting intelligence gathering missions.
The European Commission also unveiled a voluntary plan last month for its member states to deal with the influx of tens of thousands of migrants travelling to Europe via the Mediterranean.
The distribution of the migrants is expected to be agreed upon by the end of July.
Source: Al Jazeera and agencies