German media reported bloodstains could be seen on the ground and some victims were given medical treatment on trains. Photographs showed one man being treated on the platform, while another showed a man being taken away on a stretcher.
Traffic at the station had been suspended on Friday evening, with a cordon set up around the scene of the attack.
The motivation behind the attack is unclear. Germany experienced a series of knife and car-ramming terror attacks before the February federal elections.
In March, two people were killed after a man with a mental illness crashed his car into a crowd of people in the western city of Mannheim. Several others were injured.
The previous month, a rejected Afghan asylum seeker drove his car into a trade union demonstration in central Munich the day before the annual Munich Security Conference.
There was also a serious knife attack in January in Aschaffenburg, Bavaria, where an Afghan asylum seeker stabbed a 2-year-old to death in a park.
In December, a Saudi man drove his car at crowds at a Christmas market in the central city of Magdeburg, having driven through a gap in the security barriers. Six people were killed and nearly 300 injured.
Last August, in the western German city of Solingen, a Syrian asylum seeker stabbed three people to death and injured eight others during a festival celebrating diversity.
While the nationality of the suspect in Hamburg was not immediately clear, tensions have risen in Germany over the surge in attacks committed by foreigners.
The far-right, anti-migrant Alternative for Germany party secured an unprecedented 20% of the vote after February’s federal elections, making it the de facto opposition in Parliament.
