NOVI SAD, Serbia (AP) — Protesters on Tuesday threw flares and red paint on the City Hall building in the Serbian city of Novi Sad in rage over last week's collapse of a concrete canopy at the railway station that killed 14 people. Police responded by firing tear gas canisters.

The protesters surrounded the building in the city center, broke windows and threw stones and other objects despite calls by organizers to remain calm. Special police troops were deployed inside the building.

Serbia’s autocratic President Aleksandar Vucic said police were “showing restraint,” while warning that “horrific, violent protests are underway.”

“People of Serbia, please do not think violence is allowed,” he said on X. “All those taking part in the incidents will be punished.”

Miran Pogacar, an opposition activist, said “one glass window can be mended but we cannot bring back 14 lives. People are angry. Serbia won’t stand for this.”

Protest organizers said they wanted to enter the City Hall building and submit their demands, including that those responsible for the canopy collapse face justice.

Some of the protesters trying to get inside the building wore masks and were believed to be soccer hooligans who are close to the populist government.

Bojan Pajtic, an opposition politician, said he believed violence was being stoked by provocateurs, a tactic used before in Serbia to derail peaceful anti-government protests and paint the opposition protesters as enemies of the nation.

Earlier, thousands of demonstrators had marched through the city streets demanding that top officials step down because of the fatal outer roof collapse last Friday, including President Vucic and Prime Minister Milos Vucevic.

The protesters first gathered outside the railway station where they held a moment of silence for the victims as organizers read their names. The crowd responded by chanting: “arrest the gang” and “thieves.”

The protest started peacefully but some demonstrators later hurled plastic bottles and bricks at the headquarters of Vucic’s ruling Serbian Progressive Party and smeared red paint on posters of the Serbian president and the prime minister — a message that they have blood on their hands.

The protesters removed most of the Serbian national red, blue and white national flags that were apparently hung on the headquarters to prevent it from an attack. That triggered an angry reaction from the president.

“Our Serbian tri-color has been destroyed, hidden and removed by all those who do not love Serbia,” Vucic wrote on X. “Tonight, in Novi Sad, this is being done by those who tell us that they love Serbia more than us, the decent citizens of this country.”

As protests wound down later in the evening, Vucic made a surprise trip to Novi Sad and made a brief appearance before his several hundred supporters gathered outside the party headquarters.

Critics of Serbia’s populist government have attributed the disaster to rampant corruption in the Balkan country, a lack of transparency and sloppy work during renovation work on the station building which was part of a wider railway deal with Chinese state companies.

The accident happened without warning. Surveillance camera footage showed the massive canopy on the outer wall of the station building crashing down on the people sitting below on benches or going in and out.

Officials have promised full accountability and, faced with pressure, Serbia’s construction minister submitted his resignation on Tuesday.

Prosecutors have said that more than 40 people already have been questioned as part of a probe into what happened. Many in Serbia, however, doubt that justice will be served with the populists in firm control of the judicial system and the police.

Opposition parties behind Tuesday’s protest said they are also demanding the resignation of Vucevic and that documentation be made public listing all the companies and individuals involved.

The victims included a 6-year-old girl. Those injured in the roof collapse remained in serious condition on Tuesday.

The train station has been renovated twice in recent years. Officials have insisted that the canopy had not been part of the renovation work, suggesting this was the reason why it collapsed but giving no explanation for why it was not included.

The Novi Sad railway station was originally built in 1964, while the renovated station was inaugurated by Vucic and his populist ally, Hungarian Prime Minister Viktor Orbán, over two years ago as a major stopover for a planned fast train line between Belgrade and Budapest.