Vienna police banned numerous protests planned for this weekend, including one by the far-right Freedom Party on Sunday, on the grounds that protesters have generally failed to observe rules on social distancing and often not worn face masks.
Since Dec. 26, Austria has been in its third national lockdown, with non-essential shops and many other businesses closed and their staff unable to work.
The opposition Freedom Party has denounced various restrictions as "corona madness" and its leaders have sent mixed messages on issues such as vaccinations.
The affiliation of many of Sunday's protesters was not immediately clear.
Some of them, however, expressed support for the Freedom Party, and many opposed conservative Chancellor Sebastian Kurz, chanting and waving banners saying "Kurz must go" - often without wearing masks. Many carried Austrian flags.
The crowd, which police estimated at 5,000, gathered on a square in central Vienna across the central ring road from the former imperial palace as well as from the offices of Kurz and President Alexander Van der Bellen.
Rows of police in riot gear and face masks prevented the crowd from marching down the ring road.
After riots in the Netherlands apparently set off by the introduction of a night-time curfew, Austrian police avoided escalation despite having ordered the crowd to disperse, and the atmosphere was tense but peaceful.
A Reuters witness saw police make some arrests and estimated the size of the protests at thousands. Police confirmed arrests had been made without giving numbers.