"The perpetrator is under control. Police measures are continuing," Cologne police wrote on Twitter just after 3:00 pm (1300 GMT) after commandos had stormed the shop.

"A female hostage has been lightly wounded and is being cared for," they added, calling on the public to keep their distance from the area.

An AFP correspondent at the scene said he heard two stun grenade explosions as police stormed and secured the pharmacy.

Several heavily armed officers from a special response unit were seen immediately afterwards running across the Breslauer Platz square, on the opposite side of the tracks from the city's famous twin-spired cathedral.

Earlier Monday, eyewitnesses had reported hearing shots and possible smoke bombs being let off inside the massive station, which hosts many shops and cafes.

But police could not confirm any details as they rushed to evacuate the building.

Officers had later been in touch with the attacker to determine his demands and whether he was armed.

State rail operator Deutsche Bahn suspended all train traffic through Cologne, a major hub for rail travel through North Rhine-Westphalia state and nationwide.