COLOGNE, Germany—German police detained a man who took a woman hostage at the train station in Cologne on Monday and said the suspect, who was seriously injured in the rescue operation, was probably a Syrian citizen.

According to German media, the suspect identified as a member of the ISIS terror organization

Germany is on high alert for militant attacks, almost two years after a Tunisian Islamist rammed a hijacked truck into a Christmas market in central Berlin, killing 11 people as well as the driver.

"The suspect is under control," police in the western city of Cologne said on Twitter. "A female hostage has sustained light injuries and is being tended to." The suspect was being resuscitated.

A spokeswoman said officers had forced their way into a pharmacy where the suspect was, adding that the hostage-taker's motives were unclear.

The suspect is probably a 55-year-old Syrian citizen, Cologne's deputy police chief Miriam Brauns said, adding that police found identification documents in the back of the pharmacy that showed that the owner of the papers was allowed to stay in Germany until mid-2021.

The man was known to police for offences including theft and fraud, she said, adding that it was not certain that the owner of the documents was the hostage taker.

The incident prompted the evacuation of the station. "We also do not rule out a terrorist attack," Brauns said.