David Cameron has offered to commit one of the largest ships in the Royal Navy to a European operation to tackle the Mediterranean refugee crisis.

Arriving at emergency EU talks in Brussels, the Prime Minster said he was offering to deploy the Navy's flagship HMS Bulwark together with three helicopters and two border patrol vessels.

Mr Cameron stressed Britain's involvement had to take place under the "right conditions", ensuring migrants picked from the sea by the Royal Navy would not have the right to claim asylum in the UK.

"Today's meeting has got to be about saving lives. Of course saving lives means rescuing these poor people but it also means smashing the gangs and stabilising the region. Britain as ever will help," he said.

Britain would be able to contribute to all those operations in the right circumstances.

"That must include that the people we pick up and the people we deal with are taken to the nearest safe country - most likely Italy - and don't have immediate recourse to claim asylum in the UK.

"When these tragedies happen Britain is always there and this time will be no exception."

Bulwark - an assault ship - is currently in Turkey for the Gallipoli centenary commemorations and could deploy to the affected area relatively quickly.

The EU leaders gathered in the Belgian capital to discuss proposals to double the financial resources available for saving lives in the Mediterranean, where more than 1,700 migrants are feared to have died this year.

They pledged the 28 nations would "increase search and rescue possibilities" and to "undertake systematic efforts to identify, capture and destroy vessels before they are used by traffickers".

EU foreign policy chief Federica Mogherini is to immediately start preparing an operation that would likely have a military component.

Mr Cameron's call for a "comprehensive approach" to the problem has been echoed by Italian Prime Minister Matteo Renzi, whose country has rescued hundreds of refugees after their overcrowded and unseaworthy vessels have run into trouble.

Italian Defence Minister Roberta Pinotti called for refugee camps to be set up in countries bordering Libya, from where many of the boats sail, and said the Italian military was ready to go after the traffickers.

The summit was called after around 800 migrants were feared to have drowned when their boat capsized at the weekend off the coast of Libya in what the Office of the UN High Commissioner for Refugees said was the "deadliest incident" it had recorded in the Mediterranean.

European leaders have been widely criticised since the decision last year to end the Italian navy's Mare Nostrum search and rescue operation and replace it with the far more limited EU Operation Triton, patrolling the Italian coast.

On Monday the EU set out a 10-point action plan to prevent more deaths, including increase in the financial resources of Frontex, the border agency which runs Operation Triton, and an extension of Triton's operational area.

But the head of Frontex, Fabrice Leggeri, warned Triton could not be a full search and rescue operation in the way Mare Nostrum was.

"In our operational plan, we cannot have provisions for proactive search and rescue action," he said.

"This is not in Frontex's mandate, and this is, in my understanding, not in the mandate of the European Union."