Fresh clashes erupted late Saturday between protesters and riot police in Serbia's capital Belgrade and other cities, on the fifth consecutive night of unrest.
In the central city of Valjevo, where thousands had gathered to show their growing anger against the party of right-wing President Aleksandar Vucic, a small group of masked young men attacked the empty offices of the ruling Serbian Progressive Party, setting them on fire.
They subsequently clashed with riot police, with protesters throwing fireworks and rocks as the officers replied with stun grenades and tear gas, said AFP.
In Belgrade, clashes also broke out after police stopped demonstrators headed for the ruling party's headquarters.
Some clashes were also reported in the northern city of Novi Sad, the country's second largest.
Almost daily protests have gripped Serbia since November, following the collapse of a railway station roof that killed 16 people.
The tragedy became a symbol of deep-rooted corruption in the Balkan nation, with demands for a transparent investigation growing into calls for early elections.
At their peak, the protests drew hundreds of thousands onto the streets.
But the mostly peaceful demonstrations deteriorated earlier this week when large groups of pro-government supporters -- many masked and some armed with batons and fireworks -- attacked protesters.
That has sparked violent clashes for several nights, leaving many injured on both sides.
Protests were further fueled after several videos shared online showed police striking unarmed demonstrators with batons.
A video from Thursday night appeared to show around 20 officers surrounding and beating a young man in Valjevo while he laid on the ground.
Police have denied allegations of brutality, accusing demonstrators of attacking officers.
While the protests have so far led to the resignation of the prime minister and the collapse of the government, Vucic has remained defiant.
He has repeatedly rejected calls for early elections and denounced the demonstrations as part of a foreign plot to overthrow him.
