There is a general threat from terrorism. Attacks could be indiscriminate, including in places visited by foreigners. On 18 November, the Swedish authorities raised the national terrorist threat level and announced an increased police presence at public places, like airports and railway stations. See the Swedish Security Service website for more information.
On 11 December 2010, two bombs were detonated in a busy shopping area of central Stockholm. The first device consisted of gas canisters in a car and injured two passers-by. The second was a suicide device, which killed the bomber.
There is considered to be a heightened threat of terrorist attack globally against UK interests and British nationals, from groups or individuals motivated by the conflict in Iraq and Syria. You should be vigilant at this time.