Tear gas was deployed in the latest violent clash between protesters and police in Serbia.
Tensions soared in the Balkan nation on Saturday after a group of young men wearing scarves over their faces threw flares at President Aleksandar Vucic’s Serbian Progressive Party offices in Valjevo, 100km (60 miles) from the capital Belgrade.
The protesters, who were chanting slogans against Mr Vucic, set fire to the offices before clashing with riot police, who used multiple rounds of tear gas to fight and charged at demonstrators who were hurling bottles, rocks and flares at them.
There were similar clashes in Belgrade and the northern city of Novi Sad, with police also deploying tear gas after protesters set bins on fire.
In the town of Valjevo, thousands of people took to the streets to protest after a young man was injured by police who kicked him and hit him with batons.
One policeman was injured in the demonstration and 18 people were arrested so far, interior minister Ivica Dacic said.
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The protests calling for snap elections and an end to the 12-year rule of President Aleksandar Vucic have been largely peaceful in the past month before escalating to violence this week.
University students have been a key force behind nationwide demonstrations that started after a renovated rail station canopy collapsed, killing 16 people in November last year.
Many blamed the concrete roof crash on government corruption and negligence in state infrastructure projects, leading to recurring protests.
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Mr Vucic and his right-wing party have repeatedly refused the demand for an early parliamentary vote and accused protesters of planning to spur violence on orders from abroad, which they have not specified.
A former extreme nationalist, Mr Vucic has become increasingly authoritarian since coming to power more than a decade ago.
He formally says he wants Serbia to join the European Union, but critics say he has stifled democratic freedoms and strengthened ties with Russia and China.
Serbia’s parliamentary elections are due in 2027.
