Antiaircraft munitions fired by Yemen’s Houthi rebels have killed or maimed scores of civilians in Sana, the capital, Amnesty International said in a report issued on Thursday. Doctors and residents told the group that the munitions were the leading cause of casualties in the city, adding to the many dangers that have confronted civilians during the conflict between the Houthis and their allies and a military coalition led by Saudi Arabia. Airstrikes by the Saudi coalition that struck weapons depots in residential areas in the capital have also killed and wounded residents, the group found. In two recent airstrikes, residents told Amnesty that the coalition had provided no warning beforehand.