Pallade Veneta - First inmates transferred to El Salvador's new gangster prison

Bukele tweeted that "at dawn, in a single operation, we transferred the first 2,000 members to the Center for the Confinement of Terrorism (CECOT)" -- which he claims is the largest mega-prison in the Americas.

Bukele added: "This will be their new house, where they will live for decades, all mixed, unable to do any further harm to the population."

The president posted a video showing barefoot, tattooed men wearing only white boxers, bent over and with their hands behind their shaven heads.

Here they were stacked closely together, each sitting with his legs on either side of the man in front of him as armed guards in balaclavas look on.

They were loaded onto buses, hands and feet in shackles, to be taken to the new prison in a convoy that included helicopters.

At the new facility, the men were similarly stacked up before being led in large groups into their cells, where they are left sitting on the floor before stacked metal beds with no mattresses visible.

"We are eliminating this cancer from society," justice and security minister Gustavo Villatoro said on Twitter.

"Know that you will never walk out of CECOT, you will pay for what you are... cowardly terrorists," he added.

Built on Bukele's orders after he declared a "war" on gangs last March, the prison in Tecoluca, 74 kilometers (46 miles) southeast of the capital San Salvador, consists of eight buildings made of reinforced concrete.

Each one has 32 cells of about 100 square meters (1,075 square feet), designed to hold "more than 100" inmates, according to Public Works Minister Romeo Rodriguez.

Each cell has only two sinks and two toilets.

There are only 80 metal bunks for every 100 prisoners, and rights groups and observers have criticised the construction as a violation of incarceration standards.

"There will be no mattresses in the cells," the prison warden -- who wore a ski mask to protect his identity -- told journalists when the project was unveiled.

While the prison is equipped with dining halls, exercise rooms and table tennis tables, they are exclusively for guards' use.

Prisoners will leave the cell only for legal hearings by videoconference, or to be punished in a windowless and unlit isolation cell.

Some 63,000 presumed gang members have been rounded up since Bukele declared a state of emergency months ago, allowing arrests without warrants in the violence-plagued country.

M.Jacobucci--PV