Opposition politicians battling to bring down Venezuela’s strongman leader, Nicolás Maduro, have vowed to continue their struggle after the detention of one of their movement’s key figures signalled the start of a major crackdown.

Edgar Zambrano, the vice-president of Venezuela’s opposition-controlled parliament, was seized by intelligence agents on Wednesday night, and at least nine other lawmakers members are also facing detention on charges relating to last week’s failed uprising.

The politicians – all supporters of Juan Guaidó, the opposition leader spearheading the push to topple Maduro – are alleged to have committed a litany of offences including treason, conspiracy, instigating insurrection and civil rebellion.

Juan Andrés Mejía, one of the targeted deputies, told the Guardian the group would not be cowed by Maduro’s “absolutely illegal and unconstitutional” counterattack.

“This is not going to work … You are not going to solve Venezuela’s problems by persecuting and imprisoning people. There are just too many of us who want change,” said Mejía, a close Guaidó ally and member of his party, Voluntad Popular (Popular Will).

“A dictatorship is trying to advance and our responsibility is to try to stop that from happening,” added Mejía, 32.

Richard Blanco, another of the 10 targeted lawmakers, said: “They are doing this … because they are afraid. He [Maduro] knows he is on his way out.”

Blanco, 54, said he had sought shelter in the residence of the Argentinian ambassador in Caracas. “I decided to come here … because my life was in danger.”

A third lawmaker, Marianela Magallanes, has reportedly taken shelter in the residence of the Italian ambassador to avoid arrest.

The detention of Zambrano – who was among those who joined Guaidó’s fruitless attempt to spark a pre-dawn uprising against Maduro on 30 April – sparked a wave of domestic and international condemnation.

“Maduro’s arrest of … Zambrano breaches parliamentary immunity and is a clear violation of the constitution,” tweeted the British foreign secretary, Jeremy Hunt. “Feels like the act of a desperate man on borrowed time.”

The US state department slammed Zambrano’s “illegal and inexcusable” detention and warned of “consequences” if he was not freed.

Guaidó accused Maduro’s regime of “kidnapping” Zambrano, 63, who was taken to El Helicoide, a notorious political prison in Venezuela’s capital, Caracas.

The spectacular building, conceived in the 1950s as a glamorous shopping centre symbolising the wealth and swagger of South America’s oil-rich answer to Saudi Arabia, now houses the headquarters of Venezuela’s spy agency, the National Bolivarian Intelligence Service (Sebin).

That feared and shadowy organisation appears to have been poised to turn on Maduro last week, with Sebin’s director, Manuel Cristopher Figuera, defecting in order to back Guaidó.

El Helicoide serves as the headquarters of Venezuela’s National Bolivarian Intelligence Service. Photograph: by Cristóbal Alvarado Minic/Getty Images

However, for reasons that remain murky, no other major military figures joined Guaidó’s movement – despite reports that weeks of secret talks had produced an agreement that they would do so.

On Tuesday – in a clear sign that Washington thinks there may still be life in efforts to unseat Maduro – the US announced it had lifted sanctions on Figuera “in recognition of his recent actions in support of democracy and the rule of law”.

The US treasury department indicated the move was designed to influence Venezuelan officials “who take concrete and meaningful actions to restore democratic order”.

In a televised address on Wednesday night, Maduro claimed “victory” over the 30 April plotters and promised to dedicate himself to rescuing Venezuela’s collapsed economy.

“It is time for a great historic rectification of the Bolivarian revolution. It’s time for a great change in the country,” Maduro said.

Nicolás Maduro visits a farm in Aragua state in a photo released on Wednesday. Photograph: HO/AFP/Getty Images

But other top Chavistas are more cautious and warn there may be further attempts to topple their embattled leader in the days ahead – a view shared by many political observers in Caracas.

“There could be a repeat – today, in two hours, in a week, in a fortnight,” Freddy Bernal, a senior Socialist party figure, told state television on Tuesday.

Mejía also rejected Maduro’s claim to victory, while admitting the failed uprising had also not been a triumph for Venezuela’s opposition.

“He is eventually going to leave power. He has to know that at this point. He can only choose how he wants to end this – and up to now he is choosing the worst possible way,” Mejía said.

“I think there is still hope for Venezuela. I think we are on the right path. I think things are going to change. I think we are going to have a better Venezuela soon,” Mejía added.

“But if we want this to happen with the least humanitarian cost … then we have to act soon and we have to act together.”

Additional reporting by Patricia Torres