Violence flared late Saturday afternoon after crowds occupied major roads in processions that stretched for miles through the city. In several districts, people of all ages held umbrellas in drizzling rain, chanting for freedom, as social unrest stretched into a 13th weekend.

By about 5:30 p.m., police fired multiple volleys of tear gas to disperse the crowds outside the government headquarters, followed by jets of water from water cannons—some with blue dye to stain protesters. Protesters, many clad in head-to-toe black, with helmets, gas masks and shields, tossed rounds back at police and flashed laser beams in response. Some threw tear-gas canisters into the complex ...