The European police force says more foreign fighters will try to come back to Europe, and "several dozen" capable of attacks could already be there.
Their tactics could include car bombs, kidnappings and extortion, it said.
But the report plays down the likelihood of attacks on critical infrastructure, such as nuclear sites.
t says that IS militants now prefer soft targets, and there is now a greater emphasis on "lone actors" such as the perpetrator of the lorry attack in Nice in July.
