(ANSA) - Rome, February 11 - The death toll from a migrant-boat disaster in the Mediterranean has risen to at least 330 people on four inflatable rafts, the International Maritime Organisation said Wednesday. Only a handful of migrants were rescued from the vessels that set out last Saturday from Libya but hit rough seas and high winds that caused many to die of hypothermia.

The death toll continued to rise as officials realized the four vessels - not the initial two found Monday - were involved, each raft carrying about 100 people.

Overall, some 420 people were attempting to reach Europe via Italy, including 29 who froze to death, IMO Italy spokesman Flavio Di Giacomo told ANSA.

Among the nine survivors rescued by the Italian Coast Guard and merchant vessels were one minor and several people from the African countries of Senegal and Mali.

The tragedy comes amid fresh claims that the EU's Operation Triton, which took over from Italy's bigger and better-funded Mare Nostrum operation last November, is not equipped to find, rescue and treat migrants adequately.

The Council of Europe on Wednesday echoed the UN refugee agency UNHCR in saying Triton was "not up to the task".

The Triton operation run by the EU border agency Frontex was given a different mandate from Mare Nostrum, focussing instead of border security.

Critics of maritime rescue operations, such as Italy's right-wing Northern League, argue that these encourage more migrants to attempt the risky crossing from North Africa and enrich unscrupulous people traffickers.

In contrast, human rights groups and left-leaning political parties argue that migrants fleeing wars in Africa and the Middle East, particularly Syria, are so desperate they would try to flee by sea anyway.

The island of Lampedusa marks Italy's southernmost border and is often the prime destination for migrants heading for a new life in Europe.

But the treacherous seas and human smugglers have been responsible for thousands of migrant deaths each year. That demonstrates the need for a more muscular rescue agency as Triton is not equipped for the job, said Nils Muiznieks, human rights commissioner of the Council of Europe. "Europe needs an effective search and rescue system," he said. His comments echoed the chorus of voices urging the EU to strengthen its search and rescue capacity in the Mediterranean.

On Tuesday, UNHCR spokesman Adrian Edwards said that Italy had been on the right track when it established Mare Nostrum in October 2013 after two deadly migrant disasters killed some 400 migrants. "(Continued disasters) underline the need for a much more effective and improved rescue capacity in the Mediterranean to cope with the scale of the problem," said Edwards.

He also reiterated UNHCR's call for the EU to provide Italy with proper support to cope with the arrivals of thousands of migrant who make the dangerous sea crossing each year.

