NOVI SAD – Serbia’s students will lead mass demonstrations and blockades of three bridges over the Danube river in the northern city of Novi Sad on Saturday to mark three months since a concrete canopy crashed down at a train station there, killing 15 people.

The collapse on Nov. 1 of the huge concrete construction has sparked a wide anti-corruption movement and months of street student-led protests against the populist authorities in the Balkan country.

Many in Serbia believe that the collapse was essentially caused by government corruption in a large infrastructure project with Chinese state companies.

Critics believe graft led to a sloppy job during the reconstruction of the Novi Sad train station, poor oversight and disrespect of existing safety regulations.

Tens of thousands of people are expected to converge in Novi Sad later on Saturday for the blockades, dubbed “Three Months — Three Bridges.” The blockade of one of the bridges is set to extend until Sunday.

University students have taken a leading role in the protests that have developed into the most serious challenge in years to the country’s powerful populist leader, President Aleksandar Vucic.

Persistent demonstrations forced the resignation of Prime Minister Milos Vucevic earlier this week and various concessions from the populist government as it seeks to quell growing resistance.

Thousands of people already came out on Friday evening in Novi Sad to welcome hundreds of students from Belgrade who had walked for two days to join the bridge blockades.

Students from Novi Sad put a small red carpet out for the Belgrade crowd as thousands waved and many cried, illustrating high emotions over the November accident and the feeling of solidarity and togetherness in the protests.

Apart from Novi Sad and Belgrade, daily protests and traffic blockades have been held throughout Serbia, often marred by incidents, including cars ramming into protesters.

One such incident happened in Belgrade on Friday, leaving two women injured after they was struck by a car.

Carrying wreaths with the names of the 15 victims, the students from Novi Sad and Belgrade on Friday also walked together to the station building to honor the people who died in the accident.

Along the way on their 80-kilometer (50-mile) journey to Novi Sad on Thursday and Friday, the students from Belgrade were greeted by cheering citizens who honked their car horns or came out of their homes to offer food and drinks.

Hundreds more people on bicycles and motorcycles have headed separately toward Novi Sad on Friday while Belgrade’s taxi drivers said they would come too and give the marchers a lift home on Sunday.

Dung Grabos, student from Novi Sad said he felt proud of both the people from Novi Sad and Belgrade: “It’s not easy. They limp, they have blisters, their feet hurt.”

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Associated Press writers Jovana Gec and Dusan Stojanovic contributed to this story from Belgrade, Serbia.