BELGRADE, Serbia — Protesters demonstrating against the autocratic rule of Serbian President Aleksandar Vucic burst into state-run TV headquarters in Belgrade on Saturday to criticize a broadcaster whose reporting they consider highly biased.

Riot police arrived at the scene in the Serbian capital and were trying to evict dozens of people, including some opposition leaders, who had entered the downtown building. Some protest leaders said they won’t leave the building until they are given time on the main evening news.

This was the first major incident after months of peaceful protests against populist leader Vucic. The demonstrators are demanding his resignation, free elections and media, and more democracy. The protests began after thugs beat up an opposition politician in November. A former extreme nationalist, Vucic has said he wants to lead Serbia into the European Union.

Some 10,000 others also demonstrated Saturday against long-serving Montenegrin President Milo Djukanovic in the Montenegrin capital of Podgorica.

Djukanovic and his party have ruled Montenegro virtually unchallenged for three decades. He led the country to independence from much larger Serbia in 2006 and defied Russia to join NATO in 2017.

Both Vucic and Djukanovic have rejected calls to resign.

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