BUENOS AIRES—Thousands of people in several Argentine cities ransacked supermarkets for a second day in the latest challenge to President Cristina Kirchner, who is struggling to revive a weak economy and maintain her control over the ruling Peronist Party.

What started with a raid Thursday afternoon of a supermarket in the Patagonian resort town of Bariloche quickly spread to other parts of the country, with thousands of looters attacking supermarkets and shops in the cities of Rosario, Campana and Zárate. In the central...