Sweden is now on lockdown after a series of disturbing letters from the Islamic State were discovered posted on doors across the country. The message, demanding an immediate conversion to Islam, states that failure to do so would result in a steep tax or death by decapitation, according to The Express.

The letters, which pledged to murder innocent civilians in their homes if they do not convert to Islam, further states that the Islamic State would "bomb your rotten corpses afterwards." Swedish intelligence officials and authorities have already been mobilized to investigate the chilling threats.

Meanwhile, Markus Samuelsson, one of 3,000 Assyrian Christians living in Gothenburg, found the walls of his restaurant, Le Pain Francois, covered with the same message, reports The Daily Mail.

"I felt a sudden chill down my spine. It's terribly painful. We feel threatened," he said.  

The message found on Samuelsson's walls are akin to those found on the doors of Christian homes in Mosul, Iraq. The messages allowed the extremists to identify, drive out, or in some cases, execute those who lived in the dwellings.

Magnus Ranstorp, a terrorism expert, states that the city of Gothenburg has become the "Swedish Center for Jihadists," with at least 150 residents leaving the country to join the Islamic State, according to Breitbart.

With the case of the threatening notes posted on Swedish doors, however, authorities have stated that they are still unsure if the threats are real. That said, Swedish authorities pledged that they are taking the matter very seriously.

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