MADRID (AP) â¿¿ Thousands of protesters demanding the resignation of Prime Minister Mariano Rajoy demonstrated Thursday night in Madrid, and what started as a peaceful event turned violent toward midnight after riot police clashed with some protesters, resulting in at least several people arrested and injured. The protesters jammed downtown streets outside the Madrid headquarters of the ruling Popular Party, insisting that Rajoy should leave office because of allegations he received payoffs from a slush fund before his party won elections in 2011. Thousands more also demonstrated in Barcelona. Shortly before midnight, groups of protesters in Madrid clashed with police wielding batons. An Associated Press photographer saw one protester with his face bloodied, a police officer hurt by a flying projectile and at least two protesters arrested by authorities. The demonstrations came after opposition leaders this week called for Rajoy to explain himself before Parliament or face a censure vote. Rajoy on Monday brushed off demands he should resign after text messages emerged showing him comforting a former political party treasurer under investigation over a slush fund and secret Swiss bank accounts. The treasurer has claimed Rajoy took under-the-counter payments, accusations denied by Rajoy. The spectacle of alleged greed and corruption has enraged Spaniards hurting from austerity and sky high unemployment.