The anti-migrant party had organized “an open citizen dialogue” at a museum building on Cäcilienstraße, with police at hand for security.
But several dozen demonstrators “stormed the podium, chanting slogans and unrolling banners”.
“Due to the massive disturbance of the gathering, the people were led off the podium by police officers,” said police in a statement.
“But there was resistance,” they added.
“A police officer was pushed from the podium, fell and suffered serious injuries.”
The officer was hospitalized, according to the statement which did not specify the nature of his injuries.
No one was arrested but police took down the identities of 40 people who will be prosecuted for allegedly violating the law on assemblies as well as for putting up resistance against police officers.
Far-left and radical right activists often clash in Germany.
Among the most serious rampages by far-left militants took place during the G20 summit in 2017 in Hamburg.
The far-right has also shocked Germany with xenophobic riots in the eastern city of Chemnitz.