Image source, AFP/Getty Images

The surveillance programme now in place is Triton - which operates with less than a third of Mare Nostrum's budget. It is run by the EU's border agency and has a remit to patrol only Italian and Maltese waters.

It has helicopters, two aircraft and patrol boats available, and helped rescue 22,300 people between November 2014 and February 2015. But much of the criticism after today's tragedy has focused on the limited remit of Triton.

Image source, Italian Navy

Back in October 2013, after an earlier tragedy near Lampedusa, Italy's government launched Mare Nostrum - a programme with a 9.5m euro ($10.3m) monthly budget that monitored large parts of the Mediterranean.

Equipped with a thousand-strong staff, drones and helicopters, Mare Nostrum helped save 113,000 people in a year and led to the arrest of 500 human traffickers. But Mare Nostrum is no more.

Owen Bonnici, Maltese minister for justice, culture and local government

tweets, external: "EU Ministers to meet over potentially the greatest tragedy which has happened in the Mediterranean in recent years. Proactive Malta."

Richard Bilton
Lampedusa

On a boat far from land, the seas are calm and the wind light in the waters south of the tiny island of Lampedusa.

It is in these calm conditions that traffickers in Libya launch the migrant boats.

These are the deadliest waters in the world where thousands are dying.

As our boat rises and falls gently on the waves, what strikes you is the vastness of the water. It may look a short stretch of sea on a map.

But the gap between the coast of Libya and a new life in Europe is an enormous dangerous empty stretch of water with nothing from horizon to horizon.

Image source, Reuters

Italy's Prime Minister, Matteo Renzi, has travelled back to Rome from the central Italian town of Mantua, where his party was launching its election campaign, to follow the latest developments. He has reportedly called a special cabinet meeting for 16:00 local time.

Richard Galpin, BBC World Affairs correspondent, says the European Commission is "ready to provide emergency funds to Italy if Rome asks".

An EC official says if Italy makes a formal request for emergency funding to help with the issue of migration, then this could be provided immediately, but so far Brussels has not received any such request.

A request for more comprehensive assistance would require discussions with EU member states, the official says.

Image source, Reuters

Malta's Prime Minister Joseph Muscat says history will judge European nations harshly if efforts are not made to stop migrant crossing deaths in the Mediterranean.

"Although we are seeing encouraging signs from European politicians, action must be taken," he says.

"There is a tragedy going on in the Mediterranean. A time will come when Europe will be judged harshly for its inaction as it was judged when it had turned a blind eye to genocide."

Mark Micallef, chief reporter for The Times of Malta, believes the current rescue operation is "exactly what people forecasted" when the EU replaced migrant rescue operation Mare Nostrum with the Triton operation in 2014.

He says Mare Nostrum operated "very close to Libyan borders" which enabled rescuers to be "right there on the spot" in a mayday situation.

However, people had "anticipated" that Triton's new area of operation was "not where SOS' tend to happen" so rescue vessels are reaching scenes "too late", he adds.

Here's more of that interview.

Italy's coastguard confirms on Twitter, external that 28 people have been rescued and 24 bodies have so far been recovered.

Image source, Google/marinetraffic.com

To give you some sense of the scale of the search under way - here's an image showing the boats and ships searching for survivors. Towards the right hand side there is a cluster of vessels - among them are a Portuguese-registered cargo ship, a vehicle carrier from Malta and another cargo ship registered in Singapore.

Mark Micallef, a journalist with the Times of Malta newspaper, tells the BBC the number of those rescued now appeared to be as high as 50. We're waiting for further confirmation of those numbers.

Here, BBC News looks at some of the reasons why migrant crossings in the Mediterranean are so deadly - and what is driving people to take the risk.

The BBC's Imelda Flattery has tweeted an image, external of the port of Catania in Sicily, saying that many of those who drowned will arrive there later.

The Italian prime minister, Matteo Renzi, says the number of dead in the migrant boat sinking, which currently stands at 28, were provisional "but destined to grow".

He added: "How can there be beauty while every day in the Mediterranean Sea we witness a massacre, the pain of so many men and women that we pretend to forget?"

Roberta Metsola, a Member of the European Parliament from Malta, tells the BBC: "This has been going on for too long. It cannot be that every year, as soon as the seas get calmer, we hear of hundreds more deaths." She called on greater co-operation and surveillance by European countries.

"The only way to truly change the reality is to address the situation at its roots," the European Commission says.

"For as long as there is war and hardship in our neighbourhood near and far, people will continue to seek a safe haven on European shores. And as long as countries of origin and transit do not take action to prevent these desperate trips, people will continue to put their lives at risk."

The European Commission says it is currently consulting with member states, European agencies and international organisations to prepare a new European Migration Strategy, to be adopted by the Commission in mid-May.

"What we need is immediate actions to prevent further loss of life as well as a comprehensive approach to managing migration better in all its aspects," it says.

In a statement, the European Commission says it is "deeply chagrined by the tragic developments in the Mediterranean today, but also over the past days and weeks".

"The reality is stark and our actions must therefore be bold. These are human lives at stake, and the European Union as a whole has a moral and humanitarian obligation to act."

This is a map of the routes taken by those looking to leave Africa behind and head into Europe.