Venezuelan authorities have been hunting for Óscar Pérez since late last month after he claimed that he had been involved in a brazen — and bizarre — attack on two government buildings in Caracas, the capital.

On Thursday night, Mr. Pérez, a former police officer who said he had piloted a stolen helicopter used in the attack, made an audacious public appearance at an opposition rally in the capital, surrounded by a small number of masked supporters.

“It’s time for this narco-government to fall on July 18,” Mr. Pérez said in a brief interview.

He then urged Venezuelans to vote on Sunday in a symbolic referendum organized by the opposition-led National Assembly in response to President Nicolás Maduro’s plans to change the country’s Constitution.

“We will be on the streets defending the people,” he said at the rally, which honored the more than 90 people who died during the anti-government protests that have gripped the country since April.