Police in Sweden are investigating threatening letters posted through letterboxes and apparently written by supporters of Islamic State.
The letters carry the emblem of the terrorist organisation and threaten to decapitate "non-believers" unless they become Muslims or pay the "jizya" religious tax.
Dozens of the notes have been distributed in cities across the country, including the capital, Stockholm.
They say: "In the name of Allah, the merciful, full of grace. You who are not believers will be decapitated in three days in your own house. We will bomb your rotten corpses afterwards.
"You must choose between these three choices: 1. Convert to Islam. 2. Pay the jizya [religious tax] for protection. 3. Or else, you will be decapitated.
"The police will not prevent or save you from you being murdered. (Death comes to all of you)."
Swedish police and intelligence services have been analysing the notes seeking clues from the symbols and language used in them.
While extra police have been on duty in the areas targeted, no attacks have taken place.
The episode follows graffiti attacks on members of Sweden's 3,000-strong Assyrian Christian community in October. Buildings belonging to them in Gothenburg were sprayed with pro-ISIS slogans. One Christian, Markus Samuelsson, found the walls of his restaurant covered with the messages "Covert or die" and "The Caliphate is here".
Sweden has been generous to asylum-seekers, with more than 200,000 arriving this year.
However, last month it reversed its open-door policy, with the government saying it needed "respite" from the tens of thousands hoping to enter.
Prime Minister Stefan Löfven said its policy would revert to the EU minimum. From April most refugees would receive only temporary residence permits, identity checks would be imposed on all modes of transport, and the right to bring families to Sweden would be severely restricted.
"It pains me that Sweden is no longer capable of receiving asylum seekers at the high level we do today. We simply cannot do any more," he said.