The EU must sharply increase cooperation on defence and intelligence to combat Islamic terrorism and other threats, the leaders of France, Germany and Italy said, as they insisted that they were not disheartened by Britain’s historic decision to leave the bloc.

Standing on the deck of a huge Italian aircraft carrier, the Giuseppe Garibaldi, Francois Hollande, Angela Merkel and Matteo Renzi acknowledged that Europe faced the forces of “disintegration” and grave threats, including terrorist attacks, the war in Syria and the migration crisis.

It was a highly symbolic venue – the Garibaldi is coordinating the EU's migrant rescue operation in the Mediterranean, amid fears that Islamist terrorists could enter Europe by passing themselves off as refugees.

The German chancellor, who is known to back deeper EU defence plans, called for more sharing of information between European intelligence services to thwart the kind of attacks that have hit her country, France and Belgium.

“We feel that faced with Islamist terrorism and in light of the civil war in Syria, that we need to do more for our internal and external security,” Mrs Merkel said. EU countries needed to continue to cooperate in their fight against the smuggling of migrants across the Mediterranean and to protect Europe's external borders.