The prison is one of the latest measures taken by the Salvadoran government to combat crime in the country.
More than 64,000 people have been arrested since last year when a state of emergency was introduced.
The police have great freedoms to detain and eavesdrop on suspects, who no longer have the right to a lawyer, writes Reuters.
President Nayib Bukele himself shared a clip from the inauguration of the prison and expressed his satisfaction.
"This will be their new home where they can no longer cause harm to the population," he writes on Twitter.
The alarm: Innocents are arrested
Human rights activists have sounded the alarm that several people have died in police custody since the new law was introduced and that innocent people have been locked up.
Despite this, the government's measures have great support among the population, writes Reuters.
In 2015, 103 murders were registered per 100,000 inhabitants, a number that has fallen since President Bukele took power in 2019. Today, around two percent of the country's adult population is in prison.
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El Salvador's president, Nayib Bukele, is popular among the residents.
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Photo: Salvador Melendez