"The Chicago Police Department is aware and continuing to monitor this incident. While there is no actionable intelligence at this time, CPD has a special attention on the Christkindlmarket," CPD's communications office said.
Meanwhile, Aurora police have increased patrols at the city's Christkindlmarket.
The Aurora Police Department issued a statement, saying, "The Aurora Police Department is aware of the incident at a Christmas marketplace in Germany. While there is no known threat to our local Christkindlmarket, the safety of our community remains our top priority. We have had proactive measures in place, including emergency action plans, increased patrols, and coordination with event organizers. Our officers are trained to identify and respond to potential threats, and we maintain constant communication with regional and federal law enforcement partners. We encourage the public to stay alert and report any suspicious activity to on-site officers or by calling 9-1-1. Together, we can ensure a safe and enjoyable holiday season for all. The Aurora Police Department is committed to the safety and well-being of our residents and visitors. Thank you for your cooperation and trust."
A car plowed into people visiting a Christmas market in Magdeburg, Germany, on Friday, killing at least two people and injuring about 60 others, according to a German security official.
German authorities are treating the incident as terrorism, U.S. law enforcement sources told ABC News. Several people were believed to have been killed in the incident, according to the sources.
A suspect has been arrested in the attack that sent shoppers fleeing in panic, U.S. sources said.
The suspect is a doctor from Saudi Arabia who has lived in Germany since 2006, according to Prime Minister of Saxony-Anhalt Reiner Haseloff. A rental car was used in the attack, according to Haseloff.
The motive is unknown at this time, U.S. sources said.
ABC News contributed to this report.