EU foreign ministers have formally approved the launch of the first phase of a military operation against people smugglers in the Mediterranean, officials said.

The first ships and aircraft to conduct intelligence gathering missions should be available within a week, officials said on Monday.

EU foreign affairs head Federica Mogherini said the 28-nation bloc had responded quickly to the crisis

washing up on its southern shores.

"I am impressed by the unanimity and speed with which we have put this together," Mogherini said as she arrived to chair the foreign ministers meeting.

There have been serious differences among member states over how to handle the thousands of migrants crossing the Mediterranean.

Italy, Greece, and Malta have endured the burden until the loss of up to 800 people in April when their rickety boat sank and forced a rethink.

Phases of the plan

EU leaders agreed at an emergency summit that month to formulate a comprehensive plan to tackle the problem at the source, including a military option to go after the people traffickers working out of Libya.

The first phase of intelligence gathering is meant to be followed by active intervention to board and disable smuggler vessels and arrest the traffickers.

A third phase would extend these actions into Libyan territorial waters and possibly inside the country itself.

The April summit agreed that advancing to the next two phases would however require a UN Security Council Resolution and agreement from Libya before the EU would go ahead.