A distraught former Mormon missionary has posted videos on social media begging for urgent help after fellow inmates revolted and took control of a notorious prison in Venezuela.

On Wednesday, prisoners posted videos online claiming they had taken over the headquarters of intelligence agency Sebin, known as the Helicoide, where hundreds of people are held.

Inmates at the crowded Caracas detention centre – jailed opponents of Venezuelan President Nicolas Maduro – said they had taken control of the prison 'peacefully'.

Joshua Holt, a US citizen and former Mormon missionary, looking distressed while posting about riots at the Helicoide detention centre in Venezuela

Members of the Bolivarian National Intelligence Service (SEBIN) stand guard outside a detention centre , where a riot occurred in Caracas, Venezuela

A group of Venezuelan political police officers, with their faces covered, stand guard at the main door of SEBIN headquarters. Prisoner Joshua Holt said his life was threatened during a disturbance by inmates that include President Nicolas Maduro's top opponents

On social media, men identifying themselves as inmates said the detention centre, 'has been taken over peacefully by all the political prisoners and all the prisoners who are abducted here, who are tortured daily.'

One said that tear gas and weapons had been fired at detainees, but they were holding out to demand freedom.

However, a clearly distressed Utah man, Joshua Holt, who has been imprisoned for two years without trial, posted two videos on Facebook about the riot, saying his life was in danger.

In one video he said: 'I need help. So they've taken out the entire prison where I am at. The people have taken the entire prison, they're outside, they're trying to break in. They're saying they want to kill me. They're saying they want me as their guarantee. I need help. I'm calling on the people…[breaks off] '

The second clip continues: 'I'm calling on the people of America. I need your help to get me out of this place. I've been begging my government for two years.

'They say they're doing things, but I'm still here. Now, my life is threatened. How long do I have to suffer here? How long do my kids have to go on asking for their mummy and daddy. How long do I have to suffer?'

However, confusingly, in a video seen on Twitter late on Wednesday, the former missionary said: 'I'm here to show you that I am not being kidnapped. The only people who are kidnapping me is the government of Venezuela. We need the people to help us.' He was flanked by three other men.

Mr Holt said all four of them were being detained without trial and that some detainees were being denied medical attention.

His mother Laurie Holt told Reuters that she did not know the sequence of the videos and she was unable to confirm his current situation.

Mr Holt travelled to Venezuela two years ago to wed a fellow Mormon he met on the internet.

The couple were arrested at her family's apartment in Caracas after police alleged he was stockpiling weapons – an assault weapon and grenades – accusations which have been refuted by Mr Holt and his family.

Laurie Holt holds a photograph of her son Joshua Holt, who has been jailed in Venezuela for two years without trial. His family denies allegations that he was stockpiling weapons

Relatives of inmates react outside a detention centre, where a riot occurred, in Caracas. An official delegation has reportedly visited prisoners to 'respond to requests'

Members of the Bolivarian National Intelligence Service (SEBIN) stand guard next to a banner with the images of Venezuela's President Nicolas Maduro and Venezuela's late President Hugo Chavez, outside the detention centre

Venezuela's Information Ministry did not respond to a request for comment.

However, the country's Chief Prosecutor Tarek Saab tweeted: 'In the face of the events that happened in the Sebin headquarters at the Helicoide, we sent a commission of the prosecutor's office to the facility. That delegation spoke to a representative of the prisoners to respond to their requests.'

Activists said the incident had been precipitated by the beating of activist Gregory Sanabria from the state of Tachira. He appeared with a bruised face in pictures on social media.

Relatives of inmates react angrily outside the detention centre where a riot occurred. Rights groups and Maduro's opponents have said several hundred political prisoners have been unfairly jailed

A prisoner's relative wipes away tears as she awaits news of her loved one inside the notorious detention centre. Venezuelans will be voting for a new president on Sunday.

Rights groups and Maduro's opponents have said several hundred political prisoners have been unfairly jailed. Maduro has said all jailed activists were being held on legitimate charges of violence and subversion.

The United States embassy in Caracas said it was 'very worried' about the situation at the detention centre.

'Joshua Holt and other US citizens are in danger. The Venezuelan government is directly responsible for their security and we will hold them responsible if anything happens to them,' the embassy tweeted in Spanish.

Todd Robinson, the chargé d'affaires at the US embassy, went to the Venezuelan Foreign Ministry for information, the embassy added but there was, 'no response from the government.'

Venezuelans will be voting for a new president on Sunday.