Human traffickers may have rammed and sank two boats carrying nearly 700 refugees in separate incidents in the Mediterranean last week, according to the International Organization of Migration (IOM).

"If this story - which is being investigated by police - is confirmed, it would be the biggest shipwreck of recent years. It would be particularly serious as it would not be an incident, but an episode of mass killing," IOM said in a statement.

The migrants left the port of Dalmietta in Egypt on September 6. The boat, carrying nearly 500 passengers sank near Malta. Two Palestinians, who survived the drowning, were picked up by a freighter on Thursday.

"Two survivors brought to Sicily told us that there had been at least 500 people on board. Nine other survivors were rescued by Greek and Maltese ships, but all the rest appear to have perished,"IOM's spokesman in Italy, Flavio di Giacomo said.

The survivors said that they set out from Dalmietta in Egypt on September 6 and were forced to change boats several times on their way to Europe. The traffickers were on a separate boat and ordered the passengers to shift into a vessel, which the passengers feared would be too small for them.

When the passengers refused to cross over, the angry traffickers allegedly rammed the boat until it capsized, Agence France Presse quoted IOM as saying. Italian police have begun an inquiry into the shipwreck.

Meanwhile, on September 13, another boat carrying at least 250 African migrants has sunk off Libya's coast. Libyan coast guard Qassim Ayoub told the Associated Press that his country's forces were retrieving dozens of bodies still floating around 18 kilometers (11 miles) off the coast in Tajoura district. 36 migrants, including one pregnant woman have been rescued.

2,879 people have been rescued over the weekend, according to the Italian navy which is coordinating a maritime search-and-rescue mission called the Mare nostrum.

Refugee numbers have increased following conflicts in Syria, Iraq, the Middle East and Africa. According IOM figures, around 108,000 migrants had arrived in Italy by sea through late August this year, compared to around 43,000 last year.

mg/bw (AP, dpa, AFP)