A senior Sofia police official told reporters during a press briefing that protesters had again blocked roads and disrupted traffic in the city.
"Stronger, durable barricades have been erected in the capital, impeding access for ambulances and fire trucks," he said.
Tent camps have emerged at a major crossroads near Eagles' Bridge, the cobblestoned Independence Square and in between major government buildings in the downtown.
The Sofia police said demonstrators were gathering rocks and bottles and threatened to throw them at officers if they interfered.
Bulgaria, one of the poorest EU nations, has been rocked by month-long protests against the center-right government of Prime Minister Boyko Borissov. President Rumen Radev last month urged Borissov to step down after accusing his administration of corruption.