Berlin  - German police said Friday they have arrested a previously convicted far-left terrorist, Verena Becker, 57, as evidence mounted that she may have shot dead a senior public official 32 years ago.

Several members of the now dissolved Red Army Faction (RAF) were collectively convicted of the 1977 assassination of Siegfried Buback, Germany's federal prosecutor-general, and two men escorting him.

Down the years, they refused to identify the masked leftist riding pillion on a motorcycle who fired the gun.

Germans still obsessively debate the 1970s political violence, which followed student protests in 1968, and the Buback mystery. The official's son, chemistry professor Michael Buback, welcomed the prospect of a trial.

"It could bring the complete truth to light," he said, noting a witness account at the time describing the killer as petite and girl-like.

Federal prosecutors in Berlin said there was now compelling evidence that Becker, who was taken away from her suburban Berlin home on Thursday, had made an "essential contribution" to the assassination.

Becker this week denied to the mass-circulation daily newspaper Bild that she took part in the April 7, 1977 attack on Buback's chauffeur-driven car in Karlsruhe.

She has been free since 1989 after serving out a prison sentence for a different terrorist shooting,

The campaign of bombings and killings by the RAF, which dreamed of a worker uprising and a communist dictatorship, racked West Germany in the 1970s. The RAF later gave up the fight and dissolved itself in 1993.

Prosecutors in Karlsruhe said there was still no evidence Becker had been the person at the trigger, but news reports say clues were found last week in her diary.

Her DNA was also reportedly found on envelope of the RAF message which in 1977 claimed responsibility.

She was arrested in December 1977. In 1980, police dropped plans to prosecute Becker over the Buback killing for lack of evidence.

News reports claim that a year later, Becker approached police and named to them two RAF men who she said rode the motorcycle and a third man who drove the getaway car.

The arrest comes just months after a revelation that a police officer who shot dead a student in Berlin in 1967 was not a "fascist pig" as claimed by the protesters at the time, but a communist agent.

Investigators are studying whether to re-try the retired police officer, Karl-Heinz Kurras, 81, for the murder of student Benno Ohnesorg, an event which radicalized many young Germans.

The discovery in May that Kurras was in the pay of East German intelligence has led some Germans to wonder if they were misled into the 1968 revolt. He was indicted this week for illegally keeping a gun in his Berlin apartment. (dpa)