SANTIAGO (AFP) -- Three Uruguayan military officers implicated in a plot to silence a former secret police agent from Chilean dictator Augusto Pinochet's regime were extradited to Chile on Tuesday.

Retired colonel Tomas Casella, Colonel Wellington Sarli and Captain Eduardo Radaelli arrived in Santiago by military aircraft after Uruguay's supreme court agreed in March to Chile's extradition request.

It was the first time Uruguay had extradited soldiers accused of Connections to the notorious Operation Condor, a secret plan hatched by South American dictators in the 1970s to eliminate their political opponents in the region.

The three officers are accused of conspiring with their Chilean counterparts in the 1990s to kidnap and assassinate Eugenio Berrios, a former Chilean secret police agent and biochemist who had been called to testify in a human rights trial under way in Chile.

To prevent him from testifying, Chilean military officers escorted Berrios to Uruguay. But fearing for his life, he escaped his captors.

When he pleaded for help at a local police station, authorities handed him over to Casella and other Uruguayan officers in November 1992, according to court documents.

Three years later his body was found with bullet wounds on a beach 30 kilometers (19 miles) east of Montevideo. Chilean authorities believe he was killed between March and June of 1993.

During his time with the secret police under Pinochet's rule, Berrios was alleged to have prepared explosives using the nerve gas sarin and conventional bombs for planned assassinations.

Berrios has been linked to the murder of Chilean former foreign minister Orlando Letelier, an outspoken Pinochet critic, killed with an American assistant, Ronni Moffett, in a car bombing in Washington in 1975.

The three suspects, who were flown to Chile in a Uruguayan air force plane, were being detained at separate locations, Judge Alejandro Madrid, who issued the extradition request, told a Montevideo radio station.