Deputies said members of the National Guard, who provide security for the building, along with police and SEBIN intelligence agents blocked access to the opposition-controlled National Assembly.

"SEBIN agents, using the excuse that there's an explosive device within the facilities, took over the federal palace. We're surrounded by intelligence agents," lawmaker Manuela Bolivar told AFP.

Opposition leader Juan Guaido tried to incite an uprising against Maduro on April 30 but only around 30 members of the armed forces joined him, and the revolt quickly petered out. It however sparked two days of deadly clashes between protesters and security forces.

Deputy parliament speaker Edgar Zambrano was arrested by SEBIN agents last week and stands accused of "treason, conspiracy and civil rebellion."

He is one of 10 opposition lawmakers authorities have stripped of their parliamentary immunity by the Constituent Assembly, a body set up by Maduro to outflank the National Assembly, and branded traitors.

One of the 10, Luis Florido, fled to neighboring Colombia while three other lawmakers sought refuge in diplomatic facilities.

Guaido -- the National Assembly president -- has accused Maduro of trying to dismantle the legislature.

From early Tuesday, the security services cordoned off the building housing the National Assembly. Bullet-proof vehicles and a tow truck were parked in the surrounding streets.

"This is a recurring theme, it's not the first time it's happened," said Bolivar, who claimed this was part of "a policy to weaken the Assembly" and "intimidation" related to the power struggle between Guaido and Maduro, who retains the support of the armed forces.

The National Guard previously reported finding explosives when parliament opened for the year on January 5.

"Whether it's in a square, in the annex buildings, under a bridge, the Assembly will sit and there will be a session," said congressman Luis Stefanelli.

Venezuela was plunged into a political crisis in January when Guaido declared himself acting president after the National Assembly branded Maduro a usurper over his controversial re-election last year in polls widely regarded as fraudulent.

The oil-rich, cash-poor country has been stricken by recession and a humanitarian crisis in which almost a quarter of its 30 million population is in urgent need of aid, according to the United Nations.

The UN also says that more than 2.7 million people have fled the country since 2015.

Those remaining behind face shortages of basic necessities such as food and medicines, and failing public services including water, electricity and transport.