(ABC NEWS) - A car plowed into people visiting a Christmas market in Magdeburg, Germany, on Friday, killing several and injuring about 60 others, according to U.S. law enforcement sources.

German authorities are treating the incident as terrorism, U.S. law enforcement sources told ABC News. A suspect has been arrested in the attack that sent shoppers fleeing in panic, U.S. sources said.

Extensive police operations are underway at the Magdeburg Christmas market, which is now closed, local police said.