Tens of thousands of demonstrators have gathered in the Serbian capital for a fourth week, demanding the resignation of President Aleksandar Vucic following two mass massacres in and around Belgrade earlier this month.

Vucic resigned as leader of the Serbian Progressive Party (SNS) on Saturday to establish a broader political movement that he hoped would "unite a greater number of those who want to fight for the victory of patriotic Serbia."

The government of Vucic is under pressure due to the back-to-back shootings that resulted in 18 deaths and several injuries.

In the first attack in Belgrade on May 3, a teenager killed nine students and a security officer. It was the first mass murder at a school in Serbia.

The following day, a 21-year-old man murdered eight individuals outside the city.

The anti-government protesters, many of whom carried flowers and photographs of the slain children on Saturday, are furious with the ruling SNS for what they claim is a culture of violence fostered by the government and media outlets they control.

Held under the banner "Serbia against violence" and organized by opposition parties, the protests have culminated in some of the country's largest rallies since widespread demonstrations precipitated the overthrow of former President Slobodan Milosevic more than two decades ago.

Saturday in Belgrade, the crowds defied heavy rain and wind to fill the streets surrounding a compound housing the state broadcaster RTS.

Dusan Valent, a protester, stated, "I am here because I am sick of the lies and corruption." The 40-year-old told the AFP news agency, "Nothing will change until people realize it is possible and we have a choice."

They want the government to revoke the broadcasting licenses of television channels promoting violent content and prohibit pro-government newspapers that inflame tensions by targeting political dissidents.

They also demand the resignations of Interior Minister Bratislav Gasic and Security Agency Director Aleksandar Vulin.

Milica Tomic, a resident of Belgrade, stated, "If they don't meet [the demands], we're not leaving." If necessary, we will be present every day, every week, whenever.

The Belgrade correspondent for Al Jazeera, Bernard Smith, reported that protesters accused the government of encouraging a "culture of violence." He added, "They also claim the government is not doing enough to combat corruption and is moving in an authoritarian direction."

In the meantime, Vucic has accused the opposition of politicizing the shooting tragedies.

Earlier on Saturday, he resigned as leader of the SNS and appointed Milos Vucevic, the current defense minister, as his successor.

The president, re-elected by a landslide last year, has stated that his new national movement, which will promote unity and include other parties, experts, and prominent individuals, will be established in June.

"A slightly different strategy is required to unify a larger number of those who desire to fight for the victory of patriotic Serbia... A prosperous Serbia that focuses on its citizens, for a nation that does not seek for reasons for division but for unification and unity," he told an SNS Congress.

Vucic added that he would continue serving as chief of state and party member.

"I will never leave this party, and I am proud to have led the best party for all these years," he declared to a roaring audience of delegates.

According to analysts, the action attempts to regroup in the face of mounting public pressure.

The president organized a rally of his supporters on Friday to display force against the opposition-led demonstrations. The demonstration drew thousands of individuals from Serbia, Kosovo, Montenegro, Bosnia, and North Macedonia.

Vucic stated during Friday's gathering, "Those who have demonstrated in recent weeks are, for the most part, good, decent, and normal people who want what's best for Serbia."

Referring to the shootings, he said, "Those I cannot respect are the politicians who will make history with dishonor by exploiting the greatest tragedy of our people."

Long have opposition parties, and rights groups accused Vucic and the SNS of autocracy, stifling media freedoms, violence against political opponents, corruption, and connections to organized crime.

Vucic and his allies refute the charges.

In 2012, the 53-year-old succeeded Tomislav Nikolic as president of the SNS, who had held the position since 2008, when the party was founded as an offshoot of the ultranationalist Serbian Radical Party.

He initially held the positions of deputy prime minister and prime minister before being elected president in 2017 and 2022. His second and final term will conclude in 2027.

Together with its allies, the SNS controls a majority of 164 of the parliament's 250 seats.

Vucic, a fiery nationalist during the wars of the 1990s, subsequently embraced pro-European policies and made Serbia's membership in the European Union his primary objective. He also has close relationships with Russia and China.