Sweden raised its terrorism threat level on Friday based on a classified intelligence assessment, but authorities said an attack was not imminent and the threat was still low compared to other European countries.

The Swedish Security Service said it had raised the estimated threat level for terrorism targeting the country to "elevated" from "low", based on a review of security by the National Centre of Terrorist Threat Assessment.

Political violence is rare in Sweden, which has roughly 500 troops stationed in Afghanistan as part of a NATO-led force.