At least 40 migrants have suffocated to death on an overcrowded boat in the Mediterranean, the Italian navy has said today, 15 August. The migrants are thought to have suffocated when held in a confined space below deck.

The dead may have inhaled fumes from fuel after the vessel took on seawater, reported RaiNews.

The Marina Militare said it had saved 320 migrants after intercepting the boat off the coast of Libya, but that the rescue was continuing. Interior Minister Angelino Alfano said "they are still counting the victims", according to the BBC.

The Marina Militare tweeted that the ship Cigala Fulgosi was leading the today's rescue mission and recorded a video of the rescue.

The boat was said to have been in distress about 21 nautical miles (39km) off the coast of Libya.

"The dead were found in the hold," Commander Massimo Tosi, told Associated Press from the Cigala Fulgosi, adding the remains of migrants were found "lying in water, fuel, human excrement" in the hold.

Tosi said the survivors included three children and 45 women, some of whom "were crying for their husbands (and) their children who died in the crossing".

Thousands of migrants are making the journey across the Mediterranean fleeing war, persecution and poverty in the Middle East, Africa and Asia.

Recently, the crisis in the Mediterranean has been described as "beyond urgent" by European officials, as an estimated 250,000 are thought to have crossed the sea to the continent this year.

So far this year the United Nations reports that more than 2,000 migrants died attempting to make the trip by sea to Europe, including 200 feared dead after their boat capsized off Libya on 5 April.

No apology for 'migrant swarm'

Today, speaking to the BBC, Prime Minister David Cameron defended the government's handling of the Calais migrant crisis.

He stood by his use of the word "swarm" when describing the number of migrants crossing the Mediterranean, insisting voters would understand that he was not trying to dehumanise people.

"I don't regret what I said, I was simply trying to explain that a lot of people were coming from North Africa to Europe," he said. "We need to break the link between getting on a boat in the Mediterranean and getting the right to settle in Europe."

Turkish authorities reported that 2,791 migrants have been caught in the Aegean Sea in the last five days – mostly Syrians – said Al Arabiya News.

Overall, more than 33,000 migrants have been caught or rescued in the Aegean this year, according to the governor's office in Izmir.