PARIS—Terror swept the French capital late Friday as a series of attacks—in a bustling nightlife district and outside a soccer stadium—left more than 100 people dead in one of the bloodiest assaults in the country’s history.

The sheer scale of the mayhem—six separate attacks—left authorities reeling. The government declared a state of emergency, sending military forces onto the streets of Paris, sealing off roads and reinstating border controls. Sirens blared across the city as police and emergency workers rushed to respond....