One seriously injured.
mages showed emergency vehicles and armed police lined along one side of the memorial site. According to Tagesspiegel newspaper, officers had cordoned off the site and were carrying out a search.
The victim - a 30-year-old Spanish tourist - has been transported to hospital with wounds not thought to be life threatening.
Police have arrested a male suspect. It is not clear whether he was known to the victim.
Police said they did not know of any alleged motive, and several witnesses were being interviewed.
They also said they did not know what the weapon was exactly.
Many officers have been deployed to the area in the aftermath, with a police statement on X saying there are also rescue workers on site "caring for several people who witnessed the events".
The attack appears to have taken place on the northern side of the memorial - opposite which sits the US Embassy.
The Memorial to the Murdered Jews of Europe, which covers 19,000 sq metres, is described as being Germany's central Holocaust memorial.
Hours after the attack in the German capital, Swedish police said they had apprehended three men near the Israeli Embassy in Stockholm, on suspicion of preparing to commit violent crime.
"We are unable to comment on the potential motive," police spokesperson Susanna Rinaldo told the Reuters news agency.
There has been no suggestion that the attack in Berlin and arrests in Stockholm are linked.
Man seriously injured in stabbing at Berlin Holocaust memorial
