Gunmen opened fire on a prison in northern Brazil on Tuesday in an effort to aid a breakout, but an ensuing gun battle with police left 20 people dead, mostly inmates and their would-be liberators.
It wasn't immediately clear how numerous dead were inmates and how many were gunmen trying to help them escape.
Inmates are pictured on roof after a new uprising broke out at Alcacuz prison in Natal, Rio Grande do Norte state, Brazil, January 16, 2017.
They were aided by an armed group outside the jail which used explosives against one of the prison walls.
The statement added: "The attempt was supported by an extremely heavily armed group".
09 de abril de 2018, 12:57Brasilia, Apr 9 (Prensa Latina) Handwritten letters will also form part of the arsenal of agitation of supporters of former president and today political prisoner Luiz Inacio Lula da Silva, unfairly sentenced to 12 years in jail, announced Red Brasil Actual, or Current Brazil Network.
Prison guards fought back in "an intense exchange of gunfire", it said. At the conclusion of the incident, police were able to recover two rifles and five handguns at the scene.
Brazil has more than 726,000 prisoners in its notoriously violent and overcrowded prisons, which is more than the double of its total capacity of 368,000. In the worst cases, security staff are reduced to bystanders as the criminal bosses run daily life.
Last year, gang wars in prisons led to massacres that resulted in at least 125 deaths.
Prison guards took on attackers from both inside and outside the prison.
A few days earlier, at least 14 people had been gunned down at a nightclub in Fortaleza.
The appeals process can take years or even decades in Brazil's complex and backlogged legal system, offering impunity to those rich enough to afford lawyers who can launch countless technical appeals. The situation was not under control until more police reinforcements arrived.
The streets are also deadly for police: 437 were killed in 2016, the report said.