One photo from the scene shows paramedics treating someone lying on the ground, taped off by a cordon.
Police spokesman Rainer Kerstiens told The Associated Press that more suspected attackers are believed to be on the run. One of those attacked was seriously injured.
Two suspects were arrested by German anti-terror police, according to the reports.
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Terrified passengers took to social media to say the situation inside the station "looked bad" shortly after the attack.
She claimed the victim was just 13-years-old, saying: "I helped her get the wound and called her father". "Stay away from #Dusseldorf train station insane man with #axe on the lose".
Police have yet to confirm details, and there are no reports of fatalities.
Train services have been stopped or diverted at the station as the police operation continues.