Islamic State militants hope to build a maritime arm that could carry out attacks in the Mediterranean, a senior NATO Naval officer has warned, according to the Telegraph.

The march of Islamic State in Iraq and Levant (Isil) along the Libyan coast has cast an “uncomfortable shadow” across shipping, said Vice-Adml Clive Johnstone.

Vice-Adml Johnstone, a Royal Navy officer, said IS was quickly changing and had ambitions to mount seaborne operations.

He said: “We know they have had ambitions to go off shore, we know they would like to have a maritime arm, just as al-Qaeda had a maritime arm.”

As the Mediterranean is becoming increasingly militarized, commercial and tourist shipping is coming under threat, he said.

He said the growing risks to shipping in the Mediterranean mean he is “quietly worried” there will be an attack or serious incident.

He said: “I think it won’t be a planned, horrible mischievous act, I think it will be an act which is almost a mistake, or it will be an act of random terrorism that will suddenly have extraordinary implications for the Western world.”