Violent protests have erupted on the streets of Buenos Aires, as Argentina’s Senate debates the passage of a key bill that would advance President Javier Milei’s economic overhaul.

Thousands of protesters gathered in the shadow of the country’s domed Congress building on Wednesday, in a demonstration against the proposed austerity measures contained in the wide-reaching bill.

But while the day began with street barbecues, picketing and protest songs, tensions rose in the afternoon as debate unfolded inside the congressional building.

Riot police armed with helmets, batons and clear, plastic shields arrived to disperse the crowds. They deployed tear gas, rubber bullets and water cannon, spraying protesters bundled against the winter cold.

Local media reported that several opposition lawmakers who were among the crowd, including Juan Manuel Pedrini, had to be transferred to a nearby hospital to treat burns to their eyes and skin.

“A sad day for Argentinian democracy,” said a social media account for the Union for the Homeland, a Peronist political party representing the opposition.

It declared its “absolute repudiation of the repression perpetrated by the police”.

Milei’s government, meanwhile, pointed to the violent tactics some protesters allegedly used as the afternoon wore on.

Officials said 18 people had been detained after reports emerged of rock-throwing and the use of sticks as weapons. A car belonging to the radio station Cadena 3 was also set on fire.

Waldo Wolff, the minister of justice and security for the city of Buenos Aires, said one person was even found “with a grenade”.

“The culture of violence that sets the pace for demonstrations is at an end,” he wrote on the social media platform X.

“In addition to the 18 detained, we are going to take the images to the justice system so that everyone who broke sidewalks [and] burned cars and trash cans will pay.”

The administration of President Milei went further, accusing the demonstrators of attempting to overthrow the government and disrupt Congress’s proceedings.

“We went to protect Congress, and they responded with stones and fire,” Security Minister Patricia Bullrich said on X.

The social media account for the executive office issued a message as well, congratulating the armed forces “for their excellent actions in repressing the terrorist groups that, with sticks, stones and even grenades, attempted to perpetrate a coup d’état”.

The bill at the heart of the unrest — called the “Ley de Bases” or the “Law of Bases” — is set to advance Milei’s libertarian agenda, as he attempts to privatise public companies, beef up his executive powers and rev up the economy.

In Argentina, annual inflation continues to rise, currently sitting at a rate of nearly 300 percent. As costs spiral, poverty is increasing.

Milei says his austerity measures will bring inflation and the country’s sovereign debt under control — but his critics predict the steep cuts will only worsen the situation.

The bill previously passed in Congress’s lower house, the Chamber of Deputies, in late April after months of negotiations and a failed vote in February.

But political observers believe the bill faces an even higher climb in the opposition-controlled Senate. The Peronist Union for the Homeland holds 33 of the chamber’s 72 seats, compared with seven for Milei’s La Libertad Avanza party.