CARACAS, Venezuela -- Opponents of President Nicolas Maduro poured into the streets on Friday to condemn the surprise arrest of Caracas' mayor for allegedly plotting to overthrow his socialist government.

An armed commando unit dressed in camouflage entered Mayor Antonio Ledezma's office late Thursday and hauled him away amid protests by his aides. The detention, recorded by security cameras, set off a wave of spontaneous demonstrations, with Venezuelans, especially in middle-class enclaves loyal to the opposition, banging pots and pans and blaring their car horns.

A few hundred supporters gathered peacefully Friday in eastern Caracas to denounce Ledezma's "kidnapping," which they likened to the illegal capture of activists by South American military dictatorships in the 1970s. Ledezma is expected to appear in court later Friday. His lawyers said they've not yet been informed of the charges that will be levied against him.

The arrest of the 59-year-old mayor, one of Maduro's fiercest critics, comes amid a growing political and economic crisis years in the making but made worse by a recent tumble in oil prices, on which the government depends to fund spending.

Maduro in recent weeks has taken to the airwaves to rail against his opponents, accusing them of conspiring with the United States to sabotage the economy, sow unrest and carry out a coup timed to coincide with the anniversary this month of 2014 anti-government protests that caused more than 40 deaths.

As part of the crackdown, he's also seized control of a major retail chain, jailed several executives and handed more power to the military to control protests and smoke out saboteurs.

On Thursday night, Maduro went on national TV to denounce the "vampire" Ledezma, pointing to a public letter he wrote with two other hardliners calling for a transitional government as evidence that his opponents are trying to rekindle unrest.

While Ledezma's arrest may be the boldest action against his rivals, it's unlikely to rattle Maduro's core base, which is better organized and more at ease in the throes of the crisis than the perennially divided opposition, according to David Smilde, a Venezuelan researcher and senior fellow at the Washington Office on Latin America.

"The 20 per cent that are left (supporting Maduro) are pretty hardcore and Ledezma is not a likable character," Smilde said.

The embattled president could also be gambling that the allegations of a coup will enable him to distract attention from mounting woes and weaken the opposition enough to allow him to prevail in legislative elections slated for later this year.

But the growing crackdown is not without risks. Opponents, who seemed lifeless in recent weeks even as the country's problems have worsened, are enraged and Smilde says international pressure on Maduro is likely to increase.

International human rights groups were quick to condemn the arrest, and the U.S. called on regional governments to ensure Venezuela lives up to its commitments to democracy.

The U.S. State Department called the accusations of coup-plotting "baseless and false" and said they are meant to draw attention away from mounting economic problems such as widespread shortages and inflation that reached 68 per cent last year.

"The Venezuelan government needs to deal with the grave situation it faces," the State Department said in a statement.

Ledezma has been a thorn in the side of the ruling party since he was elected mayor in 2008, beating out a member of the socialist party led by the late President Hugo Chavez. The government subsequently transferred most of his powers to a newly created office run by a loyalist.

He joins another former mayor, Leopoldo Lopez, who was arrested in February 2014 for allegedly inciting the violent protests.

Government critics say that as the administration loses strength, it is becoming more dangerous.

"We are going to see new provocations and aggressions," Jesus Torrealba, spokesman for Venezuela's opposition coalition, told reporters.