Clashes erupted in Barcelona on Wednesday evening after a largely peaceful mass march against soaring housing costs, as masked groups broke away from the main demonstration and fought running battles with riot police in the city centre.

Shortly after 7.30 p.m., groups of masked protesters began throwing stones, bottles and fireworks at police near Passeig de Gràcia and Plaça de Catalunya. Rubbish bins and street furniture were set alight, creating burning barricades, while shop windows were smashed and stores were reportedly looted, including an Apple Store and a Lego store. Footage showed flames engulfing barricades as protesters confronted riot police, who responded with crowd-control projectiles and baton charges. Catalonia’s Mossos d’Esquadra police moved to disperse the groups as the disturbances spread towards Las Ramblas.

Tensions also rose in Madrid, where riot police used foam bullets, tear gas and pepper spray to disperse protesters around the central Plaza de España, according to a Reuters witness. Police reported at least 73 arrests nationwide by 9 p.m. GMT from at least 1,044 incidents linked to the general strike, including blockades of offices and industrial estates and the burning of rubbish containers. Eighteen people were arrested during the unrest in Barcelona.

The violence followed Spain’s first 24-hour general strike in 14 years, a nationwide stoppage that unions said mobilised around four million workers — roughly one-fifth of the total workforce — against the country’s housing crisis. The walkout was backed by Spain’s two largest unions, the General Union of Workers (UGT) and the Workers’ Commissions (CCOO), as well as tenants’ associations angry about rising rents and evictions. Around 120,000 people took to the streets in Madrid, while municipal police estimated more than 55,000 joined protests in Barcelona — a figure organisers put closer to 400,000.

Spain faces a housing shortfall of around 750,000 homes, a figure expected to exceed one million by 2028, according to the country’s central bank. The strike came less than three weeks before a snap general election on November 29, called after parliament rejected the government’s housing decrees in October. The protest movement was triggered by the televised eviction of 87-year-old pensioner Maricarmen Abascal on September 23, and on Thursday Congress’s standing committee is due to vote on whether to ratify the government’s reissued housing decrees.