Rome, Feb 11 (IANS): Survivors of a deadly migrant crossing of the Mediterranean Sea to Italy said more than 300 people died at sea, according to media reports Wednesday.

The survivors said they left the Libyan coast last Saturday on four inflatable boats believed to carry around 100 people each, according to Xinhua news agency.

The Italian Coast Guard, after receiving an call from a satellite phone, rescued more than 100 migrants from two of the boats struggling with freezing temperatures and eight-metre-tall waves.

Later, 29 of the rescued migrants, including a 12-year-old girl, were reported to have died of hypothermia, most of them while being transported by two guard ships to Lampedusa island, between Libya and the island of Sicily.

Italy's ANSA news agency said Wednesday that authorities were sizing up the testimony of survivors and patrolling the area where the accident was thought to have occurred.

Lampedusa, which marks Italy's southernmost border, is seen as a preferred gateway to Europe by migrants from North African and troubled Middle Eastern countries.

The UN High Commission for Refugees (UNHCR) has urged the beefing up of search and rescue operations, saying the number of migrants trying the crossing on smugglers' boats in the first weeks of 2015 was significantly higher compared to the same period in 2014.

More than 218,000 people crossed the Mediterranean by irregular routes last year and about 3,500 lost their lives in the process, according to UNHCR.