The rally's organizers from the right-wing Vazrazhdane (Revival) party posted a video of a large crowd throwing balloons filled with red paint at the EU mission’s facade.
Demonstrators waved Bulgarian national flags and placards that read "Bulgarian Constitution Above Brussels" and "NATO Out! Bulgaria is a Peace Zone."
Traffic in a central Sofia street was disrupted for half an hour and there was increased police presence in the area, the Bulgarian news agency BTA reported.