Story highlights At least 31 people have died, the Maltese military says

A dozen people or more are still believed missing, the military says

More than 200 survivors have been pulled from the water, the military says

The ship appeared to be unstable, and then capsized, the military says

The death toll from a ship that capsized Friday in international waters near the Italian island of Lampedusa climbed to 31, according to the Maltese military.

More than 200 survivors were pulled from the water, but the search continued for more than a dozen people still believed missing after the ship carrying hundreds of migrants sank, the Rescue Center of Malta, a branch of the Armed Forces of Malta, told CNN.

"We are trying to save as many people as we can," said Maltese military spokesman Keith Caruana.

Italian and Maltese military forces using helicopters and boats pulled 206 of the 250 people believed to be on board the ship, authorities said.

The shipwreck occurred in international waters about 60 nautical miles south of Lampedusa, an island south of Sicily, Italian navy spokesman Alessandro Busonero said.

According to a statement released by the Armed Forces of Malta, the ship was being followed at about 4 p.m. local time by military chase planes when it "appeared unstable."

"A few minutes later, the aircraft reported that the boat had capsized and that numerous persons were in the water. Initial assistance was provided by the aircraft, which dropped a life raft in close proximity of the persons in distress," according to the statement posted on the agency's Facebook page.

A significant number of the survivors were rescued from the life raft, Maltese authorities said

The Italian navy sent helicopters and two boats to the scene. Its sailors have rescued at least 50 people, Busonero said.

An Italian navy patrol vessel, the Libra, rescued 56 people, including nine children, the Maltese authorities said. Another 150, including 17 children, were rescued by the Maltese navy patrol vessel, P61, the Maltese military said.

It was not immediately known where the ship began its journey, and the Italian and Maltese military have not released the identities of the migrants.

Island a destination for refugees

Lampedusa, not far from Sicily and the closest Italian island to Africa, has become a destination for tens of thousands of refugees seeking to enter European Union countries -- and such deadly shipwrecks are all too common.

On October 3, a boat carrying more than 500 African migrants sank off the coast of Lampedusa, killing 309 people in what Lampedusa Mayor Giusi Nicolini called "the biggest sea tragedy in the Mediterranean Sea since World War II."

That ship originated in Libya, caught fire off the Italian coast and sank.

Survivors, many of them from Eritrea, told CNN they used bodies to keep themselves afloat until they were rescued.

The incident sparked calls for efforts to reform migration policies in the region.

A week ago Friday, the United Nations' human rights office urged the European Union to work to prevent another such incident.

The agency called on authorities to work to reduce migrant trafficking and address economic and security issues that have driven thousands of African residents to make the risky voyage to Europe in search of a better life.

Just under 115 kilometers (70 miles) from Tunisia, Lampedusa has been the first point of entry to Europe for more than 200,000 refugees and irregular migrants who have passed through the island since 1999.

In recent years, the Italian coast guard says it has been involved in the rescue of more than 30,000 refugees around the island.