Venezuelan security forces detained a key aide to opposition leader Juan Guaido in a raid on his home, an opposition lawmaker said.
Lawyer Roberto Marrero was taken by intelligence agents in the overnight operation in Caracas, said lawmaker Sergio Vergara, whose nearby residence was also searched.
Vergara said he was woken up by heavy banging at his door and agents pointed weapons at him.
Vergara and Marrero both accompanied Guaido on a recent Latin American tour to build international support for his efforts to oust President Nicolas Maduro.
Marrero heads the office of Guaido, who is leader of Venezuela's National Assembly.
"We don't know where he is. He should be freed immediately," Guaido tweeted.
The US-backed opposition leader, who had defied a travel ban to leave the country, returned to Venezuela on March 4.
The United States had warned the Venezuelan government against taking action against Guaido, who has staged frequent demonstrations in an attempt to remove Maduro.
Venezuelan prosecutors say Guaido is under investigation for alleged links to violence as well as the nation's worst power outages.
Maduro alleges the blackouts were caused by U.S.-directed sabotage, though US officials and the Venezuelan opposition say state mismanagement and corruption caused the infrastructure collapse.
The US and about 50 other countries support Guaido's contention that he is the rightful leader of Venezuela and that Maduro's re-election last year was illegitimate.
Maduro, whose key allies are Russia and Cuba, says Guaido is a collaborator in a US plot to overthrow his government.
