BRUSSELS - EU ministers said they would approve plans Monday for an unprecedented naval mission to stop people smugglers as NATO warned that militants might be hiding among the flood of migrants crossing the Mediterranean.

The ambitious operation starting in June will involve the deployment of warships and surveillance aircraft off the coast of Libya, the epicentre of the humanitarian disaster unfolding on Europe’s southern shores. The European Union’s military plan also includes the possible destruction of smugglers’ boats in Libyan waters, although that will require a UN Security Council resolution to be in line with international law. Already 2015 is shaping up as the deadliest year for refugees crossing the Mediterranean, with more than 1,800 dying this year. In total more than 5,000 have died in the past 18 months.

EU diplomatic chief Federica Mogherini said approval by the 28-nation bloc’s foreign and defence ministers at a “very intense” meeting in Brussels would help push the United Nations into action.

“I think that after we take the decision today it is more likely for the Security Council to take a resolution,” the former Italian foreign minister said, adding that the naval mission could be operational “within weeks”. Mogherini has insisted there is no question of EU “boots on the ground” in Libya, where political chaos and the rising threat of Islamic State militants make it the main launching point for people risking their lives in flimsy dinghies or overcrowded fishing boats.

Pressure has grown on governments to act after an overcrowded migrant boat sank in the Mediterranean last month, leaving more than 750 dead in a case that sparked international outrage.

But NATO head Jens Stoltenberg, also attending the meeting, warned Monday that fighters from Islamic extremist groups could also be making the crossing, posing an additional security threat.

“One of the problems is that there might be foreign fighters, there might be terrorists trying to hide, trying to blend in among the migrants,” Stoltenberg said when asked about reports IS was involved in the exodus.

Stoltenberg said that so far the 28-nation EU had not asked for help from NATO but the alliance was “ready to help if there is a request”.

Britain, France, Germany, Italy and Spain have already promised to deploy warships for the mission, a rare joint EU military venture.

British Foreign Secretary Philip Hammond said ministers needed to put together a complete programme, with the current plan “an important first step”. He said cooperation with Libya was also key.

German Foreign Minister Frank-Walter Steinmeier said he too expected ministers to approve the proposals, paving the way for initial mission planning.

A final decision, however, depends on a UN Security Council resolution, which Mogherini said she was confident would be forthcoming. “I have seen no major political resistance” during recent talks at the UN, she said.

Rights groups have criticised the military option, saying it will not solve the problem of complex smuggling networks and of a huge number of people fleeing war and poverty.

Andrew Stroehlein of Human Rights Watch said it was “utter madness”.

The headquarters of the mission, called EU Navfor Med, is to be in Rome and will be led by Italian Rear Admiral Enrico Credendino, a European diplomat told AFP.

Brussels wants to take the operation step-by-step, starting by collecting intelligence on the traffickers by using radar, satellite pictures and reconnaissance flights and raiding unflagged boats.

The naval operation is part of a wider EU blueprint launched last week which envisaged sharing the migrant burden more evenly among member states and increased cooperation with source countries to help stem the tide of people seeking a better life in Europe.

The EU has also pledged to boost funding for and step up non-military search and rescue efforts in the Mediterranean. But parts of the plan - particularly quotas for distributing asylum seeker arrivals around the EU - are causing deep divisions.

Britain says it will not take part in the quota system and has received support from France, Hungary, Poland, the Czech Republic, Estonia, Latvia, Lithuania and Slovakia.