Ecuador has declared a state of emergency in its prisons after a battle among gang members in a coastal jail in which at least 116 people were killed and 80 injured.
At least five of the dead were beheaded, AP reported. Authorities said it was the country's worst prison bloodbath.
President Guillermo Lasso decreed a state of emergency on Wednesday, which will give the government powers that include deploying police and soldiers inside prisons.
The bloodshed at the Litoral prison in Guayaquil was blamed on gangs linked to international drug cartels fighting for control of the jail.
Mr Lasso said at a news conference what had happened in the prison was “bad and sad.”
He said he could not guarantee that authorities had regained control of the prison.
“It is regrettable that the prisons are being turned into territories for power disputes by criminal gangs,” he said.
He said he would act with “absolute firmness” to regain control of Litoral and prevent the violence from spreading to other jails.
Images circulating on social media showed dozens of bodies in the prison and scenes that resembled battlefields.
Fighting involved firearms, knives and bombs, officials said.
Earlier, regional police commander Fausto Buenano said that bodies were being found in the prison’s pipelines.
Outside the prison morgue, the relatives of inmates wept, with some describing to reporters the cruelty with which their loved ones were killed, decapitated and dismembered.
“In the history of the country, there has not been an incident similar or close to this one,” said Ledy Zuniga, the former president of Ecuador’s National Rehabilitation Council.
Ms Zuniga, who was also the country’s minister of justice in 2016, said she regretted that steps were not taken to prevent another massacre after deadly prison riots in February.
Earlier, officials said the violence erupted from a dispute between the Los Lobos and Los Choneros prison gangs.
Ecuador’s president said that care points had been set up for relatives of inmates with food and psychological support. He said a $24 million programme to address the country’s prisons would be accelerated, starting with investment in infrastructure and technology in the Litoral prison.
Previously, the bloodiest day occurred in February when 79 prisoners died in simultaneous riots in three jails in Ecuador.
In July, 22 more prisoners lost their lives in Litoral, while in September a penitentiary centre was attacked by drones, although no one was killed.