The protests first started when Serbia's populist president announced a strict curfew for this weekend to curb a surge in new coronavirus cases.
Thousands joined anti-government protests in the Serbian capital of Belgrade on Saturday for the fifth consecutive day of demonstrations.
The cities of Novi Sad, Zrenjanin, Cacak and Nis had peaceful protests of their own.
Originally sparked by a decision to reimpose a lockdown on Belgrade - the unrest is now directed at President Aleksandar Vučić's coronavirus response which protesters are blaming for the second spike in infections in the country.
Critics blame the surge in cases on Vučić's decision to open the country too quickly ahead of elections which expanded his power.
Many are frustrated at the president widening his policy-making power with some saying it is authoritarian behaviour.
The demonstrations have not been led by any particular party, groups span from the left to the far-right.
Meanwhile Bulgaria is experiencing a wave of mass demonstrations against the government that began on Thursday and have kept going until Saturday night.
President Ruman Radev joined demonstrators calling on the centre-right government to step down over accusations of corruption and suppression of freedom of speech.
The protests were sparked by the chief prosecutor ordering raids on the president's headquarters and having two of his aides arrested.