CARACAS/SAN CRISTOBAL: Venezuela's streets were quieter than usual on Friday during an opposition-called strike, but participation was patchy after the socialist government threatened to shut down businesses that closed.

"The strike is a good pressure tactic ... but if I don't work, I don't eat," said insurance agent Adolfo Diaz, 38, trying to reach work despite fewer buses in the western city of San Cristobal where sentiment is strong against President Nicolas Maduro.

Venezuela's opposition Democratic Unity coalition called for a 12-hour shutdown as part of escalating protests after authorities scuttled its push for a referendum to recall the OPEC nation's unpopular socialist leader.

The government vowed to take over any companies heeding the strike, sending inspectors to ensure they were open. It posted intelligence agents outside Venezuela's main private company, beer and food conglomerate Polar, which was working normally.

Facing arrest if they encouraged the strike, business leaders said it was up to individual workers to decide.

"We are going to look for the big company owners, the leaders of (business group) Fedecamaras if they insist on a coup d'etat like in 2002," said Diosdado Cabello, the ruling Socialist Party's second in command, recalling a short-lived putsch against Maduro's predecessor Hugo Chavez.

In the capital Caracas, where hundreds of thousands of demonstrators attended anti-Maduro rallies on Wednesday, traffic was lighter than normal for a weekday and some schools were virtually empty as parents kept children home.

But businesses such as bakeries and pharmacies were open, with customary lines of shoppers seeking basics like bread and flour which have gone scarce in Venezuela's economic crisis.

"I support the opposition, but I don't agree with this strike," said Eduardo Martinez, 51, unemployed, standing near a bakery line in eastern Caracas.

EARN OR PROTEST?

Cafe owner Alfonso Brito, 54, said he opposed Maduro but could not afford to close for the day, especially given losses on Wednesday during the rallies.

"You're making people decide between earning a living or protesting," he said, adding he had fewer customers than usual.

Traffic was light and public transport fell by about half in San Cristobal, where earlier in the week masked protesters clashed with police, witnesses said. Two businesses were fined for closing, a military source said.

Parts of Maracaibo, Venezuela's second city, were deserted, witnesses said. "We have to support the Democratic Unity ... in my company we obeyed the strike," said Leydy Nava, who works for a real estate company.

Carlos Larrazabal, vice-president of Fedecamaras, Venezuela's largest corporate umbrella group, told Reuters companies were staying open and letting staff decide whether to attend or not, but troops were stationed outside various businesses.

"That should not happen in a democratic country," he said.

As well as Friday's strike, the opposition is carrying out a political trial of Maduro in the National Assembly and is vowing to march to the Miraflores presidential palace next week.

Polls show most Venezuelans want a plebiscite and that Maduro would lose if it went ahead. If he lost a referendum this year, it would trigger a presidential election and a chance for the opposition to end 17 years of socialist rule.

Despite having the world's largest oil reserves, Venezuela is suffering a third year of recession, with many skipping meals due to shortages and soaring prices.

Maduro blames the situation on a US-led "economic war" against him and the fall in global oil prices. His supporters were holding rallies on Friday to oppose the strike.

The opposition says Maduro, 53, has effectively carried out a "coup" by sidelining the legislature, arresting opponents and leaning on compliant institutions to squash the referendum. He says it is his foes who are seeking to topple him illegally.

A total of 97 people were arrested during Wednesday's nationwide protests, including seven policemen accused of rights abuses, judicial authorities said. Some 82 people were injured that day, including 26 security personnel.

"The only thing the opposition wants is to ruin the country," said Miguel Acevedo, a 48-year-old tax official, en route to work in his regulation red shirt. "Look around: today the country has said no to the opposition."