Sao Paulo (AFP) - Heavily armed men blew down the front gate of a maximum security prison in northeastern Brazil early Monday and with guns blazing enabled 92 inmates to escape while killing a policeman, authorities said.

Officials said the assault was carried out by about 20 men in four vehicles who fired on watchtowers and used explosives to destroy the front gate of the Romeu Goncalves Abrantes prison.

A policeman shot in the assault later died in hospital. There were no other reports of deaths or injuries.

The prison, a maximum security facility with 680 inmates, is located in Joao Pessoa, the capital of Paraiba state.

"Heavily armed men knocked down the main gate after an exchange of fire with police and penitentiary agents," the state's secretariat for prisons said.

By midday, 41 of the 92 escaped prisoners had been recaptured as security forces locked down the state capital, closing schools and medical centers as a precaution.

More than a thousand police officers were mobilized to take part in the search, authorities said.

State prisons secretariat head, Colonel Sergio Fonseca de Souza, said the aim of the assault was to free three suspects arrested a year ago for an armed assault using explosives.

Brazil has the world's third largest prison population, with 726,712 inmates as of June 2016, according to official statistics.

The population is double the capacity of the nation's prisons, which in 2016 was estimated to be 368,049 inmates.

"The whole of Brazil is going through this situation," military police Colonel Euller Chaves told reporters.

Along with severe overcrowding, Brazil's prisons are plagued by gang violence, and riots and breakout attempts are not uncommon.

- Violent breakouts and riots -

In April, a military-style battle erupted between guards and prisoners aided by outside associates, leaving 21 people dead at a prison in Belem, near the Amazon rainforest.

The attackers in that case also were heavily armed and tried to blow up a wall to help the would-be escapees. One policeman was killed alongside 20 prisoners and their associates.

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In February, 18 people were taken hostage during a prison riot near Rio de Janeiro, although guards managed to retake control without anyone being killed.

A month earlier, though, another prison riot in the central state of Goias ended in a blaze that left nine people dead.

A year before that, Brazilian police had to launch a massive manhunt after 184 inmates escaped from two prisons in Amazonas state following a gruesome 17-hour bloodbath between rival gangs that left 56 prisoners dead, many beheaded.

President Michel Temer then vowed to build new prisons in every state to relieve overcrowding.

But another 26 prisoners were killed, most beheaded, in another massacre in a northeastern prison later that same month, after which the government called in the army to help restore order.

The country's two biggest gangs have been at war, with much of the violence, at times savage, carried out in prisons.

In October 2016, 18 inmates were killed after violence broke out on successive days in two separate jails in the north, with some of the dead decapitated and others burned alive.