Thousands of Stasi files have already been made public

The man, identified only as Juergen G, is suspected of carrying out contract killings for a state commando unit, German prosecutors said in a statement.

German media have linked a number of suspicious deaths to the East German secret police, or Stasi, including that of a Swedish reporter in 1984.

But former East German officials deny the existence of the death squad.

The prosecutor's statement said the 53-year-old man was arrested on Monday, without giving any further details.

German media reports say the arrest is the result of years of investigation into the alleged death squad, whose existence has long been rumoured but never been proven.

'Killings abroad'

The Berliner Zeitung newspaper said the killings of people alleged by the East German communist authorities to be traitors or a threat to the regime may have been carried out abroad.

The newspaper singled out the mysterious death of a Swedish television journalist, Cats Falk, who had been investigating alleged weapons and hi-tech smuggling to East Germany.

The journalist and her friend disappeared in November 1984. Their bodies were found six months later in a Stockholm canal.

The German media have also asked questions about the death of an East German football player, Lutz Eigendorf, who was killed in a road accident after defecting to the West.

Tests showed alcohol in his blood, but his friends said he had not been drinking before getting into his car.