Scores of police officers surrounded the Occupy Frankfurt camp in a small area of park in front of the ECB's headquarters after a court rejected the activists' last-minute attempt to avert eviction.
The camp, taking its inspiration from the Occupy Wall Street movement in New York, had been set up in mid-October, making it the longest continuous protest of its kind in Europe.
Nevertheless, the city authorities had given protesters until the end of July to leave, arguing the camp had become a health hazard as it was infested with rats.
They also argued that most of the activists had long quit the camp, which had been taken over by homeless people and drug users instead and therefore had little to do with the original aim of the protests.
The court largely concurred with the authorities' arguments, but gave the activists two weeks to appeal the ruling.
Police said the camp's 60 or so inhabitants – who included an estimated 20 activists – were asked to leave voluntarily, otherwise they would be removed by force.
However, surrounded by crowds of onlookers and media, the clearing of the camp proceeded mostly peacefully, aside from one protester who shouted "Dictatorship! Police state!", according to an AFP reporter at the scene.
Maike Wolf, 24, who said she had been at the camp since October, told AFP that the protestors were "extremely disappointed" and described the police action as "totally over the top."
"The evacuation violates the constitution and the right to assembly. We will take this to a higher court," she said.
Emanuel Rauber, 29, who also said he has been in the camp since October, complained that the "homeless and the Roma" who had joined the camp "won't have a roof over their heads any more."
But he added that "we can start all over again once this has all been cleared. So it's not that bad. We'll either come back here or squat an empty house. It's a new beginning," he said.
Some of the protesters helped the police clear the tents and load the refuse onto lorries.