Mediterranean migrant deaths: PM calls for action after boat disaster
David Cameron has described the boat disaster in the Mediterranean as a "dark day" for Europe.
The prime minister blamed "appalling human traffickers" for the deaths of up to 700 migrants off the coast of Libya on Sunday.
Mr Cameron said a "comprehensive" approach was needed to tackle the problem. He will attend an emergency summit of European leaders on Thursday.
Labour leader Ed Miliband said rescue patrol operations should be restarted.
Mr Cameron spoke to Italian PM Matteo Renzi by phone on Monday and backed his call for an emergency European Council meeting on the migrant crisis.
UK Foreign Secretary Philip Hammond and Home Secretary Theresa May met with other EU ministers in Luxembourg on Monday to help form a series of measures to ease the situation.
It was decided at the meeting that the EU's Triton patrolling service would be strengthened with extra funding and an increased operational area.
Ministers also discussed measures to help resettle migrants in their home countries and to destroy vessels used by people smugglers.
Meanwhile Italy and Malta said they were working on the rescue of at least two migrant boats in the Mediterranean, with hundreds on board, after new distress calls were received.
Mr Cameron said: "This has been a dark day for Europe; it really is horrific the scenes that we've all witnessed on our television screens, the loss of life.
"We've got to deal with the instability in the countries concerned, we've got to go after the human traffickers and the criminals that are running this trade.
"We've got to make sure yes, there is an element of search and rescue, but that can only be one part of this and we should use all the resources we have, including our aid budget which can play a role in trying to stabilise countries and trying to stop people from travelling."
The prime minister has also said: "Britain can do more and lend a hand, and in that spirit I'll be going to the European council meeting on Thursday"
But Labour leader Ed Miliband said search and rescue operations in the Mediterranean should be restarted.
"Europe has got to learn the lessons because we can't have people drowning in European waters in this way, the world standing back aghast and Europe standing back," he said.
The European Union withdrew funding for the "Mare Nostrum" search and rescue operation last year, replacing it with a much smaller scheme known as Operation Triton.
UKIP leader Nigel Farage said the UK's foreign policy was partly to blame for the crisis.
"The fanaticism of [former French president] Sarkozy and Cameron to bomb Libya - and what they've done is to completely destabilise Libya, to turn it into a country with much savagery, to turn it into a place where for Christians the situation is virtually impossible," he told the BBC on Sunday.
"We ought to be honest and admit we have directly caused this problem."
Migrants rescued 10-17 April
Feared to have died attempting the crossing so far this year
35,000 Migrants have arrived from North Africa in 2015
218,000 Estimated to have crossed the Mediterranean in 2014
3,500 Migrants died attempting the crossing last year
Liberal Democrat leader Nick Clegg rejected Mr Farage's comments and accused him of trying to score political points.
The deputy prime minister said: "I think the humanitarian reasons why not just ourselves, but other countries, decided to intervene from the air in Libya is well-known.
"Gaddafi could not have been more explicit - he said that he was going to kill every innocent man, woman and child in Benghazi.
"To suggest that intervention is the sole reason for the very profound economic and social dislocation and poverty in the whole of North Africa is both simplistic and taking election-time political point-scoring to a new low."
Mr Renzi said on Monday that his country was working with Malta to rescue at least two boats in distress. He said one of the vessels was a dinghy off the Libyan coast with about 100-150 people on board. The other was a larger boat, carrying 300 people.
Another vessel carrying dozens of migrants has run aground off the coast of the Greek island of Rhodes, killing at least three people, including a child, the Greek coastguard has said.