Thousands of demonstrators, mainly students, poured through the streets of Belgrade on Friday, in preparation for what will likely be one of the largest protest rallies against the government in years. Many had come from far away some on bicycles, others on foot to participate in the burgeoning protest against President Aleksandar Vucic’s government.

Live video showed crowds waving and cheering Serbian flags as student groups entered different Belgrade suburbs before gathering in the city center. The protests, which started following a fatal railway station roof collapse in Novi Sad where 15 people died on November 1, have also expanded to incorporate teachers, farmers, and workers. The protesters attribute the accident to negligence and government corruption.

As tensions mount, Vucic’s outgoing Prime Minister, Milos Vu evic, who has already resigned in protest at the crisis, made a blunt threat of violence, warning that authorities will use force if provoked. “The state has the machinery of force please do not provoke it,” Vu evic warned in a TV address.

At the same time, Vucic’s allies have also made mobilizations, establishing camp outside his office and positioning tractors around their protest site.

The demonstrations were originally calloused by student protests for disclosure of information on the railway station tragedy, such as the release of pertinent documents and prosecuting those liable. Although the authorities have indicted 13 individuals and disclosed an anti-corruption policy, protest organizers are not convinced and continue demanding wider political reforms.

The head of the Serbian Orthodox Church, Patriarch Porfirije, called on all sides to abandon violence, and Vucic’s office said the president would speak to the country at 6:00 p.m. (1700 GMT). With tensions running high, the next few days could be decisive for Serbia’s future.