Nearly 490 alleged members of the powerful Central American gang Mara Salvatrucha (MS-13), including several alleged leaders, went on trial collectively in El Salvador on Monday, accused of thousands of murders.

El Salvador is conducting mass trials of thousands of suspected gang members, many of whom have spent years in prison without charge or visiting rights, as part of the anti-gang crackdown of iron-fisted President Nayib Bukele.

The Attorney General's Office said 486 suspected MS-13 members were on trial for 47,000 crimes committed between 2012 and 2022, including 29,000 homicides.

The country's court system said the trial included "members of the national leadership, street-level leaders, program coordinators from across the country, and founders of" MS-13.

Salvadoran authorities accuse the group of a range of crimes, including the killing of 87 people in a single weekend in March 2022.

In the wake of those killings, Bukele, a close ally of President Trump, declared a "war" on gangs, which he said controlled 80 percent of Salvadoran territory.

MS-13 is charged with the crime of rebellion "because they sought to ... establish a parallel state," the Attorney General's Office said.

"We are going to put them on trial, and we are going to settle a historic debt," prosecutors said.

Bukele in 2022 imposed a state of emergency that's been used to arrest more than 91,000 suspected gang members, including thousands who were later declared innocent.

The campaign, which made Bukele hugely popular, has resulted in a dramatic decrease in crime, turning El Salvador from one of Latin America's most dangerous countries to one of its safest.

Rights groups, however, have denounced what they say are gross human rights abuses, including a lack of due process for the detainees, reports of torture and more than 500 deaths in prison.

Same sentences for all

The fates of the detainees are now being decided in mass trials, with anonymous judges handing down one-size-fit-all punishments to large groups of defendants following the proceedings via video-link from prison.

MS-13 and the rival Barrio 18 gang operate drug trafficking rings and extortion rackets across Central America.

The Trump administration has declared the two groups -- among others -- terrorist organizations, designations it has used in part to justify deadly military strikes on alleged drug-running boats.

The two gangs were born among Salvadoran youth on the streets of Los Angeles and then spread back to El Salvador, where they have terrorized the population for more than three decades.

Bukele has accused them of murdering 200,000 people, including about 80,000 who disappeared without a trace.

State prosecutors said they had "ample evidence to request the maximum sentences" against the defendants, without specifying whether that meant life imprisonment.

At the opening of the trial, the judge stated that armed groups had disturbed "the peace of the Salvadoran population and the security of the state" for decades, and would be tried "with the full force of the law."

New York-based Human Rights Watch (HRW) and regional NGO Cristosal have criticized the mass trials, warning of the risk of innocent people being made to pay for the crimes of the guilty.