Belgrade and some other Serbian cities have seen mass demonstrations since two deadly shooting rampages in early May that killed 18 people and wounded 20 others, including elementary school pupils.
Tens of thousands of people rallied again in downtown Belgrade on Friday, demanding the resignation of Serbia's populist president and warned of "radicalisation" of the peaceful protest if their demands aren't met — all in the wake of two mass shootings that stunned the nation.
The protesters carried posters of President Aleksandar Vucic and his close ally Prime Minister Ana Brnabic dressed in black-and-white striped prison uniforms.
They chanted the slogan "Vucic Go Away" and protest leaders said their demands, which include the resignation of top security officials and the withdrawal of national broadcasting rights to pro-government TV stations that promote violence, must be met by the end of the next week.
They said that if their demands were not fulfilled by the deadline, the peaceful protests will assume a new, more radical form. They didn't reveal what the "radicalisation" of the protests could include.
The protest on Friday was the sixth in the Serbian capital since the May killings.
"We cannot return the lives to the victims, but we can make sure that this doesn't happen again," actor Milan Maric said while addressing the crowd. "We want Serbia without violence, Serbia with hope."
The opposition has accused Vucic of fueling intolerance and hate speech against his opponents during his increasingly 11-year autocratic rule, while illegally seizing control of almost all state institutions. Vucic has denied this, saying that opposition groups want him toppled by force or even killed.
The Serbian president earlier this week promised an early parliamentary election, in an apparent attempt to defuse the growing public discontent with his rule. Most of the opposition parties, however, have rejected holding an election while Vucic maintains a firm grip on almost all leverages of power, including the mainstream media.
The two shootings on 3 and 4 May stunned the nation, especially because the first one happened in an elementary school in central Belgrade when a 13-year-old boy took his father's gun and opened fire on his fellow students. Eight students and a school guard were killed and seven other people were wounded. One more girl later died in hospital from head wounds.
A day later, a 20-year-old used an automatic weapon to randomly target people in two villages south of Belgrade, killing eight people and wounding 14.
A new protest is planned for next week in what is becoming an increasingly serious challenge to Vucic, perhaps the biggest one he has faced since coming to power.