Police said the demonstrations exceeded the maximum of 50 people allowed to gather under rules aimed at stopping the spread of the coronavirus.
Daily Aftonbladet said that around 80 demonstrators had gathered on each of the bridges.
A third demonstration took place outside an office building in the west of the city.
“Overall, in all these three places, there has been no violence at all,” a police spokesman said, adding that some demonstrators had been physically removed from the two bridges.
Representatives from Extinction Rebellion said they were protesting against politicians’ failure to deal with global warming and called on the government to declare a “climate emergency.”
The government has a target of being the first fossil free developed economy with zero net emissions by 2045 at the latest.
By Simon Johnson