CARACAS — Venezuela's opposition denounced a "parliamentary coup" after a rival to Juan Guaido declared himself parliament speaker on Sunday as security forces prevented the incumbent from entering.

Images of Luis Parra declaring himself head of the chamber by megaphone were shown on state television channel VTV, as Guaido and fellow opposition lawmakers were blocked from entering the National Assembly.

Guaido had been expected to be re-elected parliament speaker in a vote on Sunday but only regime lawmakers and opposition deputies critical of Guaido were allowed to enter the building.

"ALERT! Parliamentary coup. Without votes, nor a quorum PSUV (socialist party) deputies are trying to swear in a false leadership," said the National Assembly on its Twitter account.

Guaido had earlier hit out at President Nicolas Maduro's regime for preventing numerous deputies and journalists from entering the National Assembly — the only government branch in opposition hands.

"Today, those who help to prevent the legitimate installation of the Venezuelan parliament are converting themselves into accomplices of the dictatorship and of those oppressing the Venezuelan people," Guaido wrote on Twitter.

Guaido has led the National Assembly for the last year.

But when he arrived Sunday morning he was prevented from entering by police carrying out a security operation.

Ahead of Parra's self-proclamation, opposition deputy Jose Brito, an opponent of Guaido's, told journalists that Parra would stand against the current speaker.

"You could have been the future — now you are and will be the past," Brito told journalists, addressing Guaido.

Both Parra and Brito fell out with Guaido last year after being accused of corruption related to the over-pricing of imported food.

Guaido sprang to prominence a year ago when he declared himself acting president in a direct challenge to Maduro's authority during a crippling economic crisis.

Parliament had branded Maduro a "usurper" over his controversial 2018 re-election in a poll widely denounced as fraudulent. — AFP