LA SIBUCARA, Venezuela—Hours after they looted and set fire to a National Guard command post in this sun-baked corner of Venezuela earlier this month, a mob infuriated by worsening food shortages rammed trucks into the smoldering edifice, reducing it mostly to rubble.

The incident was just one of numerous violent clashes that have flared in pockets around the country in recent weeks as Venezuelans wait for hours in long supermarket lines for basics like milk and rice. Shortages have made hunger a palpable concern for many...