Masked intelligence agents have arrested a key aide of Venezuela’s opposition leader, Juan Guaidó, in an apparent sign that the embattled president, Nicolás Maduro, may be cracking down on challenges to his rule.

Dozens of officers from the Sebin intelligence service broke down the door of Roberto Marrero’s home early on Thursday and took him to El Helicoide, a notorious political prison overlooking Caracas. The home of opposition legislator Sergio Vergara was also raided.

Guaidó, who has been recognised by the United States and 50 other nations as Venezuela’s legitimate leader, told reporters that the crackdown was a sign of Maduro’s “weakness”.

“As they cannot take the interim president prisoner, so they seek out people closest to him, threaten relatives, carry out kidnappings,” he said.

Maduro, who has overseen a dramatic collapse of Venezuela’s economy, has said Guaidó should “face justice” but has not explicitly ordered his arrest.

The interior, justice and peace minister, Néstor Reverol, said in a video statement that Marrero and his bodyguard Luis Alberto Paéz had been arrested for fomenting an insurrection.

“This citizen [Roberto Marrero] was seized with weapons of war and numerous foreign currency in cash,” Reverol said. He added that Marrero was part of “a criminal network that wanted to carry out terrorist attacks in the country.”

The US quickly condemned Marrero’s arrest, which was defined by Donald Trump’s national security adviser, John Bolton, as a “big mistake”.

Maduro has made another big mistake. The illegitimate arrest of Roberto Marrero, Interim President Juan Guaidó’s aide, will not go unanswered. He should be released immediately and his safety guaranteed. — John Bolton (@AmbJohnBolton) March 21, 2019

The secretary of state, Mike Pompeo, said on Twitter that the US “will hold accountable those involved”.

Marrero described the raid in a voicemail message forwarded by Guaidó’s team. “I am in my house and the Sebin is here. Unfortunately, they have come for me. Keep up the fight, don’t stop and look after [Guaidó],” Marrero said.

Photographs that circulated on social media showed Morrero’s house in disarray after the raid.

Marrero had previously worked as a lawyer for Leopoldo López, a well-connected opposition leader thought to be the architect of Guaidó’s rise, who was arrested in 2014 after leading protests against Maduro. López has been under house arrest since July 2017.

At a protest outside the Sebin headquarters, the parliamentarian Guillermo Luces said: “This is an attack against the free world that supports our president Juan Guaidó.”

Luisa Ortega Díaz, the country’s former chief prosecutor who broke with Maduro in August 2017, also denounced the arrest. “The tyranny today began the execution of a plan of progressive arrests and the sowing of evidence against leaders of the opposition.”

The move against Marrero followed a fact-finding mission by the United Nations’ top human rights official, Michelle Bachelet, who accused Maduro of clamping down on dissent.

“Whenever there is the presence of the international community the government of the usurper Maduro reacts with this type of activity,” Luces said.

Since January, Venezuelan authorities have arrested over 1,000 people in connection with anti-government demonstrations, most of them arbitrarily, rights groups say.

On Wednesday, Bachelet also warned the UN human rights council that recent US sanctions on Maduro’s inner circle threaten to deepen Venezuela’s crisis, but she said that the country’s “pervasive and devastating economic and social crisis” started before the US first levied sanctions.

Venezuela’s economy has collapsed over recent years, with hyperinflation rendering the currency useless while shortages in food staples and medicines are commonplace.

The country has been mired in a political crisis since late January when Guaidó, a previously unknown politician, declared himself the legitimate interim president.

Maduro, who retains the support of the country’s armed forces, has repeatedly denied the existence of a crisis in his country, blaming instability on an “economic war” waged by the US.