Assyrian Christians living in Sweden have been targeted with a string of threatening messages linked to the Islamic State, including demands that they “convert or die.”

A recent report by Swedish daily Dagens Nyheter revealed that the Assyrian community in the city of Gothenburg, in southwestern Sweden, is being menaced by unidentified aggressors using known Islamic State methods and symbols. According to reports, local police are investigating the threats, but so far have found nothing.

The town of Gothenburg is a hotbed for jihadist recruiting, and the Swedish newspaper Aftonbladet earlier this year reported that at least 150 people had left the city to join the Islamic State in Iraq and Syria. Terrorism expert Magnus Ranstorp has called Gothenburg “the Swedish Center for Jihadists,” and the town with a population of a half million has contributed more fighters to ISIS than the entire United States of America.

On Tuesday, Swedish Assyrian Markus Samuelsson found the walls of his restaurant in Gothenburg covered in jihadist graffiti, including messages of “Convert or Die” and “The Caliphate is Here.”

These same messages, along with the ISIS logo and the Arabic letter ن, were painted on the walls of the Le Pain François bakery and the next-door pizzeria as well, though other, non-Assyrian owned restaurants were left untouched.

“I felt a sudden chill down my spine. It’s terribly painful, we feel threatened,” Samuelsson, who owns Le Pain François, told DN.

ISIS militants in the Middle East have used the Arabic letter ن to signify Christians—Nazarenes—and painted it on the doors of Christian homes in Mosul before seizing the city last year. Identifying the homes of Christians, Islamic State fighters later drove them out of the city, telling them to either leave, convert to Islam, or pay a tax.

Samuelsson is one of some 3,000 Assyrian Christians living in Gothenburg.

In February, an essay in the Sweden Report complained that when defecting Swedes return to their homeland after serving as ISIS militants in the Middle East, they are not punished by Swedish authorities, but are “coddled with therapy” and “fast-tracked to jobs ahead of native Swedes.”

Just last week, the Islamic State released a video showing three Assyrian Christians being killed in Syria, and ISIS fighters have warned that they will kill 180 more if a ransom isn’t paid.

Last Easter, as Assyrian Christians were celebrating the feast, militants from the Islamic State booby-trapped the 80-year-old church of the Virgin Mary in Tal Nasri village in the western countryside of Hasaka province, in northeastern Syria, blowing it to pieces.

The Assyrian Church of the East is one of the oldest branches of Christianity, with roots dating back to the 1st century AD. Assyrian Christians speak Aramaic, the language of Jesus, and have their origins in ancient Mesopotamia, a region that extends across northern Iraq, north-east Syria and south-eastern Turkey.

Follow Thomas D. Williams on Twitter @tdwilliamsrome