The air force commander of Libya's internationally recognised government has 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 on Monday to launch a naval operation to combat people-traffickers who have brought thousands of migrants on perilous journeys across the Mediterranean Sea to Europe.
Securing consent from Libya, where two rival governments and their armed forces are battling 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 late on Monday.
The self-declared National Salvation government, set up last summer when an armed faction called Libya Dawn took over the capital, has also expressed its "deep concern" over the EU plan.
In a statement on Tuesday, the Tripoli government interior ministry said the EU had not taken into consideration the difficult situation within Libya nor how to coordinate with Libyan authorities for example on returning migrants.
The EU naval initiative will be limited to intelligence-gathering - using submarines, warships, drones and helicopters - for now because it has yet to obtain the United Nations' authorisation for a wider scope of operations.
The initial plan was to disrupt the traffickers' business and to capture and destroy their ships, possibly even in Libyan waters.
But the EU would need a U.N. Security Council resolution and consent from the Libyan authorities to operate in Libyan territorial waters and coastal areas and it has neither so far.
The United Nations is trying to broker a ceasefire and power-sharing deal between the two factions as Western governments worry Libya is becoming a safe haven for militants as well as for smugglers ferrying illegal migrants into Europe.