At least 29 prisoners were killed and 19 police wounded in clashes at a jail in western Venezuela Friday, authorities said.

The incident at the police station jail in the town of Acarigua, some 220 miles (350 kilometers) from the capital of Caracas in Portuguesa state, occurred when police special forces (FAES) tried to stop a "massive prison break" which resulted in the deaths of 29 inmates, according to Portuguesa public security secretary Oscar Valero.

The prisoners received the officers with "a hail of gunfire" while detonating three grenades, which injured 19 police, Valero told reporters.

The Una Ventana a la Libertad NGO, which defends prisoner rights, gave a preliminary toll of 25 dead.

NGO director Carlos Nieto said the clashes broke out when the FAES attempted to rescue visitors who had been taken hostage Thursday by the "pran" -- the leader of the inmates -- at the jail.

"This morning (authorities) sent the FAES and there was a clash. The detainees had weapons, they shot at the police. Apparently they also detonated two grenades," Nieto told AFP.

The inmates' leader, Wilfredo Ramos, was one of those killed, according to an internal police report.

The report, quoted by the NGO, said several officers were wounded by "shrapnel and explosives."

The prisons ministry did not comment on the incident, saying police station jails are not under its control.

A video shared on social media shows an inmate -- believed to be Ramos -- with his face partly covered while brandishing a pistol and what appears to be grenades, and threatening two women.

"It's our lives (on the line) and those of the visitors here," he says, as a woman pleads for help, while warning the police to stay out because "I'm prepared to die."

Nieto said the inmates were demanding "food and to be transferred to prisons," and had denounced police "abuses."

No information was given about the fate of the hostages.

Venezuela is in the throes of a historic crisis marked by shortages of food and medicine that's driving millions to flee the country. Critics say about 30 prisons spread across Venezuela are severely overcrowded and run by gangs that traffic drugs and weapons.

Violence is a problem in such detention facilities, where inmates are supposed to be held for a maximum of 48 hours, Una Ventana a la Libertad said.

There are around 500 of them in the country, holding 55,000 people even though their total capacity is just 8,000, the NGO added. The Acarigua jail has capacity for 60 inmates but was holding 500, according to the police report.

These provisional detention centers "are not suitable to hold inmates for more than 48 hours," said Nieto. He said the prison system as a whole is "chaotic" and blamed the prisons ministry for "not fulfilling its functions."

Venezuela has one of the worst records for prison violence in the region. In March 2018, 68 inmates died in a fire at a police jail in the northern city of Valencia. And in August 2017, a riot at a facility in the southern Amazonas state left 37 prisoners dead.

More than 400 people are believed to have been killed in Venezuelan jails since 2011, while human rights organizations also say they face a lack of food and medicines -- like much of the country -- while the facilities are beset by corruption.

"For how long are Venezuelan prisoners in the state's hands going to die?" said Humberto Prado, director of the Venezuelan Prisoners Observatory NGO, who branded Friday's events a "massacre."