Buenos Aires, December 20 (RHC)-- Argentina's Congress has passed a pension reform measure, as demonstrators and police fought pitched battles outside the capitol building while the country's main union called for a 24-hour general strike against the widely-opposed proposal.

Lawmakers narrowly approved the sweeping changes to the country’s pension system, voting 128-116 on Tuesday.

Conservative President Mauricio Macri, elected in 2015 with an agenda of slashing currency and trade controls favored by his development-oriented predecessors, says Argentina needs pension reform to slash its deficit and attract investment. His government promoted a pension reform that will reset the system for calculating pensions for around 17 million people. According to opposition figures, the government will save around $5.6 billion by slashing the pensions.

Debate on the bill was suspended last week due to massive demonstrations also backed by workers' unions. While Macri promised to decree a bonus payment to the “neediest” retirees, opposition and union organizers continued to mobilize massive numbers of Argentines to the Congress as lawmakers resumed debate on the proposal.

Protesters were met with water cannons and tear gas and fought back using slingshots to fire rocks at police, turning the vast lawn in front of the capital into a battleground. "This bill will put millions of retirees at risk. It changes the whole pension system," Laura Rivas, a 34-year-old teacher told reporters, standing back from the site of most violent protests. "We are going to have to work more years before we can retire, and then the pension payments we get will be minimal, so it hurts us as workers."