(CNN) A van slammed into a crowd Saturday in an apparently deliberate act in the German city of Muenster, killing two people and leaving 20 others injured, officials said.

The driver also shot and killed himself, a police spokeswoman said. The driver was a German citizen, said Herbert Reul, state minister for internal affairs in North Rhine-Westphalia state.

Authorities are treating the incident as an attack. There is no known connection to radical Islam but investigators are still looking into the driver's background, Reul said.

Police earlier said there were three deaths. Reul clarified later Saturday that the total included the attacker.

Muenster police spokesman Andreas Bode said law enforcement is looking into witness reports that some people fled the attacker's van after the attack. He also said there was a suspicious object in the vehicle that was under investigation.

Bode said the motive of the driver is unknown.

The attack happened in the old part of the western German city, an area popular on weekends. It was a warm sunny afternoon, one of the first nice days of spring, and many people were out in the area with its narrow streets, Bild editor Julian Reichelt told CNN.

German Chancellor Angela Merkel said she is "deeply shocked by the terrible events in Muenster."

In a statement tweeted by German government spokeswoman Ulrike Demmer, Merkel said "everything is now being done to clarify the act and support the victims and their families."

The driver drove a vehicle into a restaurant's open terrace around 3:30 p.m. local time, according to police spokeswoman Vanessa Arlt.

Arlt said the old city remains closed, and police have asked people to avoid the city center.

Muenster, with about 300,000 people, is home to numerous universities and has a student population of about 58,000, the city government says. The city calls itself the cycling capital of Germany and says about 100,000 residents use a bike daily.

Firefighters walk through downtown Muenster, Germany, on Saturday after a vehicle drove into a crowd.

"With dismay, I learned of the terrible incident in Muenster," Interior Minister Horst Seehofer said in a statement, adding, "Police in Muenster and throughout (the state of North Rhine-Westphalia) are now working hard to investigate the matter."

Federal authorities are in close contact with local officials, Seehofer said.

The White House sent condolences in a statement from press secretary Sarah Sanders.

"Our thoughts and prayers go out to the families of those killed and we wish a full recovery to those injured. While the German authorities have not yet announced a motive for this cowardly attack on innocent people, we condemn it regardless, and pledge any support from the United States government that Germany may need."

Saturday's crash occurred on the one-year anniversary of a similar attack in Stockholm, Sweden, when a stolen beer truck struck pedestrians, killing five people.