Police and gang members have clashed in the Brazilian city of Rio de Janeiro for a fourth day, despite further raids by security forces. At least 15 people were reported killed on Wednesday as police sought to quell the wave of gang violence. Heavily armed men continued to stop cars and buses, rob passengers and set vehicles alight, police said. Officials say drug traffickers are fighting back against police operations aimed at pacifying city slums. “There are groups of criminals who have been installed here for 20, 30 years, and they might not want to give up,” said Rio state public safety director Jose Beltrame.