(AP-ANSA) - BELGRADE - Thousands in Serbia protested again Saturday against populist President Aleksandar Vucic as riot police deployed inside the country's parliament, saying they wanted to prevent the opposition from storming the building. The protest in central Belgrade in front of the parliament building - the biggest so far in 19 straight weeks - came after months of anti-government demonstrations accusing Vucic of being autocratic and demanding that his government allow more democracy, media freedoms and free elections in the Balkan nation. Opposition leaders, ranging from the far-left to right-wing, said authorities sought to prevent their supporters from coming to Belgrade for the rally Saturday. Police denied the accusations. Speakers called for a prolonged struggle against Vucic's government and demanded that the European Union stops what they called its support for his rule. Although staunchly pro-Russian, Vucic has claimed he wants to take Serbia into the EU. Opposition leaders said they want to speak with the government about democratic changes, including free media and free elections, adding that if Vucic refuses, they will gather again in Belgrade next Saturday. Vucic's conservative party members, meanwhile, barricaded themselves inside the Belgrade parliament building and in local city councils throughout Serbia on Saturday, claiming they wanted to prevent the forceful takeover of power by "fascists and thugs." Tensions have mounted all week as pro-government media and officials alleged that the opposition wanted to storm state institutions and take power by force. Those comments came despite the fact that the weekly anti-government protests have been largely peaceful. Vucic, who denies accusations that he's an autocrat, said Saturday's protest "will achieve nothing" and added that any trouble makers "will be removed" from the streets. The anti-government protests started after masked thugs beat up an opposition politician last November. Late Serbian hard-line leader Slobodan Milosevic was ousted from power in 2000 after protesters stormed the parliament in Belgrade. Vucic was his close associate then. Vucic plans to bring his supporters to Belgrade next Friday to counter the rising revolt against his rule. DUSAN STOJANOVIC/ (AP-ANSA)