An American film-maker was formally charged late Saturday by Venezuelan officials who accuse him of paying right-wing groups to foment post-election unrest on behalf of US intelligence.

The federal prosecutor's office said Timothy Tracy, 35, of West Hollywood, California, was charged with crimes including conspiracy, association for criminal purposes and use of a false document.

On Thursday, President Nicolas Maduro said he had personally ordered Tracy's arrest on suspicion of "creating violence in the cities of this country" in the wake of a 14 April presidential election narrowly won by the hand-picked successor to Hugo Chávez.

Opposition candidate Henrique Capriles contends the election was stolen from him by fraud, setting up post-election tensions and bitter accusations between Venezuela's government and opposition.

Friends say Tracy is an innocent, self-funded documentary film-maker with no political aims or government ties.

The US government has also said Tracy is innocent but declined comment on the specifics of his case.

Venezuela's national prosecutor's office said a judge had ordered Tracy held until further notice in a jail run by the national intelligence service in the capital, Caracas, because he presented a risk of flight.

Tracy had a translator and private lawyers hired by him, or on his behalf, during the hearing, prosecutors said.

The Georgetown University English graduate was a story consultant on the 2009 documentary American Harmony, about competitive barbershop quartet singing, and produced the recent Discovery Channel program Under Siege, about terrorism and smuggling across the US-Canada border as well the History Channel series Madhouse, on modified race-car drivers in North Carolina.

Separately, Venezuelan officials said Saturday that they have arrested a retired general who had become a fierce critic of the government, a detention the opposition called part of a hardening crackdown in the wake of the disputed election.

Retired brigadier general Antonio Rivero gained fame for denouncing Cuban involvement in the Venezuelan military in 2010 and became a prominent member of the opposition, participating in post-vote protests this month.

Rivero appeared in a brief video of a post-election protest that prosecutors played for the press Thursday after announcing Tracy's arrest. They said the video was taken from Tracy's belongings, along with another short video that shows a group of young people talking, in what appears to be a joking, sarcastic manner, about being paid many millions of dollars to participate in anti-government demonstrations.

In a snippet that is clearly heavily edited, Rivero discusses demonstrators' use of clubs and rocks in a clash with National Guard members. It is unclear, because of the editing and brevity of the clip, whether he is encouraging them to use weapons or discouraging them.

The footage appeared to be taken at a protest in Caracas soon after the vote results were announced, in which university students and National Guard members traded rocks and tear gas.

Leopoldo Lopez, national coordinator of the opposition Voluntad Popular party, called Rivero's detention illegal and part of a campaign to arrest and "morally assassinate" Venezuela's opposition leadership.

"The government errs if it thinks we are going to falter in our just solicitude that the truth be known about the April 14" election, Lopez said. Rivero is a member of Lopez's party.

Venezuela's Public Ministry released a statement saying that Rivero would be presented before a tribunal "for his presumed connection to violent acts that have occurred recently in this country".

The statement said the retired general was arrested by Venezuela's intelligence service on Saturday.

The government says post-election attacks by Capriles supporters killed nine members of the ruling Chavista movement, left dozens injured and damaged government offices and medical clinics.

The opposition vehemently denies the accusations.