Assyrian Christians in Gothenburg have been threatened with messages linked to Islamic State, according to local reports. Swedish Daily Newspaper 'Dagens Nyheter' (DN) reports that ISIS symbols and other graffiti were found painted on two stores owned by Assyrians on Tuesday. Along with the ISIS logo, "the caliphate is here", "convert or die" and the Arabic letter 'N', ?, were also painted on the walls of the Le Pain Francois bakery and the next-door pizzeria. Short for Nazarene, ? was painted on homes belonging to Christians by ISIS militants in Mosul when it was captured last year to identify members of the faith. Jihadists later drove them out of the city, telling them to either flee, convert to Islam, or pay a tax. Those who refused were killed. "I felt a sudden chill down my spine. It's terribly painful, we feel threatened," Markus Samuelsson, who owns Le Pain Francois, told DN. "Our family fled Turkey for Sweden in the 70s. What we're exposed to reminds us of the stories we were told as children. It's very real and threatening, and we're terrified." Chairman of the Assyrian district in Gothenburg, Josef Garis, told DN that the police are investigating the case. "The persecution of the past feels near," he said. Earlier this year, Swedish newspaper Aftonbladet reported that at least 150 people had travelled to Iraq and Syria to join ISIS from Gothenburg. Terrorism expert Magnus Ranstorp has called the city "the Swedish Center for Jihadists", despite it having a relatively small population of 490,000. Last week, ISIS released a video showing three Assyrian Christians being killed in Syria, and militants have threatened to kill 180 more if a ransom isn't paid. An ancient branch of Christianity, the Assyrian Church of the East has roots dating back to the 1st century AD. Assyrian Christians speak Aramaic, the language of Jesus, and have origins in ancient Mesopotamia -- a territory which spreads across northern Iraq, north-east Syria and south-eastern Turkey.