In the latest incident, Italy's navy and coast guard, as well as a passing cargo ship, intervened overnight to rescue 364 people from an overcrowded fishing boat that had capsized in stormy waters north of Libya.
Six dead bodies were also picked up, and the search was continuing for more survivors, the Italian navy said, adding that since Friday nearly 4 000 migrants had been rescued from the central Mediterranean.
On Saturday, a navy patrol boat picked up 73 people and recovered 18 bodies from a dinghy off the island of Lampedusa. It had suffered engine failure was being battered by heavy seas.
In Libya, navy spokesperson Ayoub Abul Qassem said on Monday that least 200 people died in a Friday shipwreck, adding that the search was on for the missing.
The wooden boat was carrying African migrants and only 17 had survived so far.
"The navy lacks the resources and qualified personnel," Abul Qassem told dpa. He said the current political violence across Libya increased difficulties facing officials in dealing with illegal immigration.
Human traffickers
Since the ousting of Muammar Gaddafi in 2011, Libya's rulers have struggled to re-establish security. The country has become a main point for human traffickers who smuggle people from African countries to Europe across the Mediterranean. Most boats head for Italy.
So far this year more than 100 000 migrants have landed on Italian shores, a record number. Rome authorities have launched a maritime search-and-rescue operation to prevent deaths at sea, but they say they cannot continue funding it on their own.
Interior Minister Angelino Alfano has called on the European Union to take over the Mare Nostrum (Our Sea) mission. He was expected in Brussels on Wednesday for talks with EU Home Affairs Commissioner Cecilia Malmstrom.
"I am appalled by these new tragedies at sea and I express my condolences to the victims and their families," Malmstrom said on Sunday. "The European Commission remains committed to help Italy in its efforts," she added.
Italy is also clamouring for a change in EU asylum laws, allowing refugees to be spread across the bloc. But Germany and other northern countries, which already take in far more asylum-seekers than Italy, are opposed.