Serbian President Aleksandar Vučić on Sunday vowed to take "tough measures" against what he called "rioters" following a wave of widespread anti-government protests, in which he accused some participants of committing "terrorist acts". Thousands of people took to the streets in several cities on Sunday evening, including the capital Belgrade, chanting slogans calling for the "arrest of Vučić" and the release of all those detained in recent days. In a televised address, Vučić renewed his claims that the months-long protests against his rule were "orchestrated by the West" and aimed at "destroying Serbia", the Associated Press reported. "Our country is in grave danger. They have endangered all our values, our normal lives, and every single one of us," Vučić said, claiming there was a "well-orchestrated plot" ultimately aimed at installing "left-wing anarchist" authorities. "Unless we take tougher steps, it's a matter of days before these people kill someone. I say this for the historical record," Vučić added. "You will see the determination of the Serbian state. We will use everything we have to restore peace and order in the country." Vučić did not specify what response the state would take but clarified that declaring a state of emergency was not currently being considered. Protests escalate The president's stark warnings came after five consecutive nights of confrontations between protesters, police and his supporters. On Saturday evening, angry demonstrators set fire to the offices of the ruling Serbian Progressive Party in a western town, as well as the offices of its coalition allies. Further clashes erupted in Belgrade and the northern city of Novi Sad, where riot police used tear gas against demonstrators who threw stun grenades and Molotov cocktails. The escalation in clashes follows more than nine months of largely peaceful protests that began after a train station roof collapsed in the north of the country, killing 16 people. Many blame the tragedy on widespread corruption in government infrastructure projects. Serbia is officially seeking to join the European Union, but Vučić has simultaneously maintained close ties with Russia and China. On Sunday, he praised Russian support for his government against what he described as a "colour revolution" aimed at overthrowing him. Speaking to state broadcaster RTS, Vučić said those seeking to destabilise Serbia are not based in the country, but abroad, and criticised domestic political elites for slowing economic growth. "Our economy is growing more slowly than it should, due to the irresponsible behaviour of part of the political elite and unrest deliberately provoked by certain actors. This is largely instigated from abroad," he said. He indicated that elections would be held when necessary and could occur early if required, and reaffirmed Serbia's support for the Republika Srpska in Bosnia and Herzegovina, saying the country would not interfere in its internal affairs or elections. The president also announced that measures to curb rising prices would be introduced within the next ten days.