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 Wayuu Indians who live here at the northern tip of Venezuela’s 1,300-mile border with Colombia.

The soldiers had been deployed to stem rampant food smuggling and price speculation, which President Nicolás Maduro blames for triple-digit inflation and scarcity. But after they seize contraband goods, the troops themselves often become targets of increasingly desperate people.

“What’s certain is that we are going very hungry here and the children are suffering a lot,” said María Palma, a 55-year-old grandmother who on a recent blistering hot day had been standing in line at the grocery store since 3 a.m. before walking away empty-handed at midday.

In a national survey, the pollster Consultores 21 found 30 percent of Venezuelans eating two or fewer meals a day during the second quarter of this year, up from 20 percent in the first quarter. Around 70 percent of people in the study also said they had stopped buying some basic food item because it had become unavailable or too expensive.

Food-supply problems in Venezuela underscore the increasingly precarious situation for Mr. Maduro’s socialist government, which according to the latest poll by Datanálisis is preferred by less than 20 percent of voters ahead of Dec. 6 parliamentary elections. 

The critical situation threatens to plunge South America’s largest oil exporter into a wave of civil unrest reminiscent of last year’s nationwide demonstrations seeking Mr. Maduro’s ouster.

“It’s a national crisis,” said Marco Ponce, head of the Venezuela Observatory of Social Conflict, noting that unlike the political protests of last year, residents are now taking to the streets demanding social rights.