Forces from Libya's internationally recognised government have warned European countries that any vessels entering Libyan waters without permission would be targeted by air strikes.

The warning came after European Union foreign ministers agreed yesterday to launch a naval operation to combat people smugglers who have brought thousands of migrants on perilous journeys to Europe from Libya.

Securing consent from Libya, where two rival governments and their armed forces are battling in a chaotic power struggle for control, has been a major concern for European powers trying to stem an increasing flow of migrants from Libya's shores.

"Any vessel found in Libyan waters without previous cooperation or permission will be targeted by the air force," Libyan air force commander Saqr Al-Jaroushi told Reuters.

The EU naval operation will be limited to intelligence-gathering for the time being because it has yet to obtain United Nations authorisation for a wider scope of operations.