Around 20,000-30,000 Bulgarians took part in political rallies for and against the embattled Socialist government on Saturday, according to a media tally.
Some 10,000-15,000 gathered in the capital Sofia in support of Prime Minister Plamen Oresharski, who has braved months of demonstrations calling for him to resign.
In the central city of Plovdiv a similar size rally was organised by the opposition conservatives, who were in power until resigning in February after nationwide protests.
In the capital there was a heavy police presence to prevent clashes with and among football fans attending a nearby match between arch crosstown rivals Levski and CSKA.
Students, who have occupied Sofia University for the past two weeks calling for Oresharski to resign and staged a parliamentary blockade this week that turned violent, stayed inside the university for fear of being attacked.
"I came to back the cabinet! It was not given any chance to work, to show what it can do by all these street demos and students protests," pensioner Dima Shopova, 60, told AFP as she waved a big Bulgarian flag in Sofia.
"I don't want my children to be ruled by the communist mafia," an elderly man told public BNR radio in Plovdiv.
Six years after joining the European Union, Bulgaria remains the bloc's poorest member. Brussels had repeatedly criticised Sofia over corruption and oligarchs influencing politics.