A police officer who stole a helicopter and fired on two Venezuelan government buildings appeared in public for the first time on Thursday night, defying a nationwide manhunt by showing up at a protest in the capital.

Except in videos posted on the internet, Oscar Perez hadn't been seen since he shocked the nation on June 27 by using a stolen helicopter to fire grenades and gunshots at the supreme court and interior ministry buildings. The government called it a "terrorist attack".

Perez spoke briefly to journalists at a Thursday night vigil to honour the more than 90 people killed during three months of demonstrations against Venezuela's government.

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He urged Venezuelans to vote en masse on Sunday in a symbolic referendum being organised by the opposition to oppose President Nicolas Maduro's plans to rewrite the constitution. Perez said the vote should mark the start of a sustained street campaign to force the embattled socialist leader from office.

"It's the zero hour," Perez said as several masked youths looked on from behind. "The true way to pay respects to those who've died is for this dictatorship to fall."

He screamed, "What does Venezuela want?" That drew shouts of "Freedom!" as he raised his fist and hopped on the back of a motorcycle that sped off into the night.

In several videos, Perez has declared that he belongs to an uprising of members of the security forces who are fed up with Maduro's administration. Even though he had vowed to appear at an opposition rally, many people believed he had fled Venezuela following a nationwide manhunt in which the stolen helicopter was located near the Caribbean coast outside Caracas.

Perez's stunt shocked many in Venezuela, although some suggest it was a false flag operation by the government to distract from the crisis.

So far there has been no evidence backing Perez's claim that an uprising is under way among security forces, even though Maduro frequently warns that the opposition is trying to woo the military into a US-backed conspiracy to remove him from power.

Perez's colourful past has mesmerised Venezuelans. Perez, 36, is also an action film star who portrays himself as a James Bond-cum-Rambo figure on social media. A trained pilot, he starred in a 2015 film, "Suspended Death," and his Instagram account is full of photos showing him in fatigues, bearing assault rifles, skydiving and standing in action poses with a German shepherd by his side.

His appearance at the rally came as a few hundred people braved steady rainfall on Thursday night for a march in which they stopped at several spots in eastern Caracas where young protesters have been killed during the recent unrest.

Venezuela is undergoing a major crisis as hundreds of thousands of people have taken to the streets in recent months calling for an end to Maduro's presidency, amid food shortages, a collapsing currency and soaring inflation.