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Reuters
Thousands of people are protesting in Belgrade against the Serbian leader Aleksandar Vucic.
Rallies - largely peaceful - have been staged outside the president's official residence since the end of last year.
But tensions escalated on Saturday when followers of the #1od5miliona movement stormed the state TV station.
As angry crowds gathered outside his residence on Sunday, footage was released of Mr Vucic inside, playing chess with the interior minister.
Mr Vucic, a reformed extreme nationalist who now wishes to lead Serbia into the European Union, previously said he would not bow to opposition calls for media and electoral reform.
However, he did say he was willing to call a snap election to test his party's popularity.
What happened on Sunday?
Riot police fired tear gas at crowds that gathered outside the presidential residence on Sunday, as they blew whistles and shouted "Resign!" and "He is finished!" at the building.
"He is finished" was the slogan of the movement that ousted Slobodan Milosevic in October 2000.
President Vucic gave a televised address from inside, in which he proclaimed: "I am not afraid."
"Serbia is a democratic country, a country of law and order and Serbia will know how to respond," he added, branding the protesters "fascists, hooligans and thieves".
"They think they have the right, 1,000 of them, to determine the fate of the country," Mr Vucic added, probably underestimating the number of protesters involved.
After the president's address, crowds of people marched from the residence to the city's main police station, demanding that the people who were arrested at the Radio Television of Serbia (RTS) building on Saturday night be released.
Once they arrived, they were again locked in a stand-off with riot police outside the front door of the station.
How did the protests start?
In November last year, the opposition politician Borko Stefanovic - leader of the Serbian Left - was beaten up and left unconscious by a group of young men in dark clothing.
Images of his bloodied face and clothes sparked waves of protests in Belgrade.
Opposition leaders blamed President Vucic for the attacks, and accused him of bringing back an autocratic style of rule reminiscent of the Milosevic era - despite his claims to want to take Serbia into the EU.
Critics also accused the president of reviving nationalism and hate speech in the country.
Who is leading the protests now?
Now, one of the most prominent figures in the opposition protest movement is Bosko Obradovic, the leader of the extreme right-wing party Dveri.
He was among those who occupied the public broadcaster RTS's building on Saturday and, according to Balkan Insight, was physically dragged out of the building by police officers.
"We aren't asking for much," Mr Obradovic demanded at the station. "An immediate broadcast with participation of a representative of the organisers of the protests, not of politicians."
Mr Vucic has called Mr Obradovic "a fascist".