Berlin police on Sunday broke up a protest against coronavirus curbs and opened an arson investigation after an attack on a building housing the country's public health agency.
Hundreds of police officers were out on the streets of the German capital to monitor a protest of some 2,000 people claiming the government's measures to curb the virus undermine their freedom.
The demo was timed to coincide with the opening of the three-day World Health Summit in Berlin where the pandemic will be the main topic of discussion, although the event has been moved online this year because of the virus.
Berlin police on Twitter said they broke up the protest early because participants failed to comply with social distancing rules and face mask requirements.
The demonstrators shouted slogans such as "We are the people" and "We are here, we are loud because they are robbing us of our freedom".
Some of them were confronted by counter-demonstrators who shouted "Nazis out!".
Separately, police in Berlin said they had opened an investigation into attempted arson after "several people who remain unknown" were seen overnight throwing "incendiary devices" and bottles at a building belonging to the Robert Koch Institute (RKI) for disease control.
The attack caused a small fire that a security guard was able to extinguish and no one was hurt, the police statement said. The facade of the building suffered minor damage including a broken window pane.
Police said they were not ruling out a political motive for the attack, given the RKI's high-profile role in communicating to the public about the coronavirus and advising the government on its pandemic response.
The tensions come as Germany grapples with a spike in coronavirus cases after having coped relatively well with the first wave in the spring.
On Sunday, the RKI reported more than 11,000 new cases over the past 24 hours, marking the fourth day in a row the country has crossed the 10,000 mark.
Overall, Germany has recorded 429,181 Covid-19 cases since the start of the pandemic and 10,032 deaths.
The cities of Frankfurt and Erfurt announced at the weekend that they were cancelling their popular Christmas markets this year to help slow the spread of the outbreak.
Chancellor Angela Merkel's centre-right CDU party meanwhile said it was considering postponing its December 4 congress for 1,000 delegates, who are set to choose a new party leader and possible Merkel successor.