Two Venezuelans firemen who made a viral video portraying President Nicolas Maduro as a donkey were jailed on Sunday pending trial on charges of inciting hate and could face up to 20 years in prison if convicted, right groups said.

Ricardo Prieto, 41, and Carlos Varon, 45, were arrested by military counterintelligence officers on Wednesday at the fire station where they worked in western Merida state, according to the human rights observatory of the University of the Andes in Merida, which is tracking the case.

The pair appeared on Sunday before Judge Carlos Marquez, who ordered they be held for trial on charges of violating a law against fomenting hatred that was passed last year, the observatory and the Penal Forum rights group said.

"The firemen were indicted with an aggravated charge of inciting hate. That aggravated charge indicates ... 20 years of jail time," said lawyer Ivan Toro of the observatory, who attended the hearing.

Opponents of the leftist Maduro, who blame him for Venezuela's economic meltdown, have long dubbed him "Maburro" in a play on the Spanish word for donkey, "burro."

His administration did not respond to a request for comment on the case. Reuters was not immediately able to contact Prieto and Varon or their lawyers.