The protests started as somber vigils for the victims. After spending a freezing night out in the open, hundreds of striking students on Friday resumed their two-day anti-graft protest march from the capital, Belgrade, to the northern city of Novi Sad, where they plan to blockade three bridges over the River Danube this weekend. The bridge blockade is planned for Saturday to mark three months since a huge concrete construction at the railway station collapsed in Novi said on November 1, leaving 15 people dead.

What started two months ago as a protest against suspected corruption in construction contracts has developed into the most serious challenge in years to the country’s powerful populist leader, President Aleksandar Vucic. Along the way to Novi Sad, the students were greeted by cheering citizens, honking their car horns or coming out of their homes with offers of refreshments and food. When they reached the town of Indjija on Thursday, roughly halfway along their 80-kilometer (50-mile) route, they were welcomed with fireworks and cheers from residents.

Although most of them spent the night out in the open in a soccer field, the freezing temperatures did not dampen their desire for major changes in the corruption-ridden Balkan state. Nevena Vecerinac, a student, said she hoped the protesters’ demands that include the punishment of all those responsible for the rail station tragedy will be fulfilled.“We will make it to Novi Sad,” she said. “Yesterday’s walk was easy. It’s cold now, but we can make it. We all have the same goal.”“We need support from all people. With this energy and mood I hope we can do it, otherwise there will be no brighter future,” said Luka Arsenovic, another student marcher.

If Serbian President Aleksander Vucic hoped the resignation of his hand-picked prime minister would get students to end nearly three months of anti-corruption protests, he didn’t have to wait long for an answer. Hours after Milos Vucevic stepped away on Tuesday from his role leading the country’s government, thousands of protesters poured into the streets of Serbia‘s second-largest city, Novi Sad, to resume their calls for political change that have seriously shaken Vucic’s decadelong populist rule for the first time.

The daily protests began after the massive concrete canopy hanging over the entrance to Novi Sad’s newly renovated central railway station collapsed on November 1, killing 15 people. They have become increasingly raucous, serving as way for people to vent their unhappiness with Vucic’s authoritarian rule and reflecting their growing demands for transparency while the country increasingly undertakes large infrastructure projects, mostly with Chinese state companies.

Critics allege that corruption, poor oversight and substandard construction caused the tragedy. But state officials have offered few details about the project’s finances or provided conflicting information, including whether any work was done on the station’s roof and overhang. After the prime minister’s resignation failed to quiet the protesters, Vucic sharpened his rhetoric, issuing veiled warnings against them and suggesting his and his supporters’ patience was running out.

The protests started as somber vigils for the victims, but grief quickly gave way to anger at demonstrations in Novi Sad and elsewhere. Professors, doctors, actors and farmers have joined the university students in staging several huge rallies, including one in front of the Serbian state TV in the capital, Belgrade, that continues to take an uncritical view of the government despite demonstrators’ demands for unbiased reporting.

Protesters have been holding daily 15-minute traffic blockades throughout the country. They honor the 15 people who died, including two children, and begin at 11:52 a.m., the time the overhang collapsed. Chants such as “corruption kills” also marked the protests that demanded the dissolution of the entire government over the tragedy. Protesters left symbolic handprints in red paint on government buildings, accusing authorities of having “ blood on their hands.”Several incidents have marred the demonstrations, including drivers twice ramming into crowds and injuring two women. A young woman was also attacked by Vucic supporters with bats this week, suffering a broken jaw.

The students are demanding full transparency about what caused the collapse and for anyone found responsible to face justice. Although students have refrained from naming specific targets of an investigation, Vucic’s political opponents have suggested that anyone who might have had a hand in the renovation deal, if it was corrupt, should stand trial, singling out Vucevic, who led Novi Sad’s local government before becoming prime minister.