EU foreign affairs head Federica Mogherini said Thursday the bloc could step up action against people smugglers in the Mediterranean within weeks, seizing and destroying boats to break up their networks.

The EU launched a first, intelligence gathering phase of its EU NavFor Med operation in July and Mogherini said she had told bloc defence ministers meeting in Luxembourg that it had met all its objectives.

"I proposed to the defence ministers to discuss the transition to phase two ... to the capture and destruction of vessels," she said.

"The proposal would mean that the operation (would go ahead) once a decision taken and capacity raised, hopefully in a few weeks."

"I see a broad consensus on the need to start phase two," she added, highlighting the wider crisis which has seen hundreds of thousands of migrants fleeing war and turmoil in the Middle East and North Africa risk their lives to get to the European Union.

Mogherini said EU foreign ministers meeting in Luxembourg Friday and Saturday would take up the issue, with formal approval to follow shortly.

These phase two operations would still be confined to the high seas in line with international law, she stressed.

A third phase in the military operation, agreed by EU leaders after more than 700 migrants drowned off southern Italy in April, would allow EU NavFor Med to take action against people smugglers inside Libyan territorial waters.

This step however requires at a minimum a UN Security Council resolution and preferably Libyan government agreement.

Mogherini said the EU continued to work on getting a resolution and cited signs of progress after Russia said Wednesday the Security Council was discussing a draft which could be adopted this month.

However Russia's UN ambassador Vitaly Churkin said the resolution would only cover action taken on the high seas.

"We have stated and decided from the very beginning ... that we would always act within the framework of international law," Mogherini said.

EU efforts to help establish a national unity government in Libya have so far failed to bring the warring factions there together but a fresh round attended by both was scheduled for Thursday in Geneva.

EU NavFor Med currently comprises four ships -- one Italian, one British and two German -- and would likely need several more for the enlarged mission.