The prison administration indicated, in a statement, that
the officers intervened quickly and found a detainee wounded with knives. He was taken to the hospital and is currently in stable condition.
The statement did not name Sirhan, but a US government source confirmed that it was Sirhan Sirhan.
The alleged perpetrator has been identified and isolated pending an investigation. We do not know the motives behind his gesture.
Sirhan, 75, was convicted of shooting Kennedy shortly after midnight on June 5, 1968.
Robert F. Kennedy, then Democratic senator from New York, was campaigning for the presidential election. He had just finished his California primary victory speech at the Ambassador Hotel, since demolished in Los Angeles.
The senator then went through the kitchens to get out of the hotel and that's where the killer shot him three times. Reached the head, Kennedy died the next day.
Five people were also wounded in the shooting.
Sirhan was sentenced to death. But the California authorities later commuted his sentence to life imprisonment.
He was denied parole several times.
A Palestinian of Jordanian nationality, he has claimed over the years that he did not remember shooting at Kennedy.
In a television interview, he said he felt betrayed by Kennedy's support for Israel during the Six-Day War of 1967.
Like the murder of his brother John F. Kennedy in 1963, several questions remained unanswered in the investigation into the death of Robert F. Kennedy.
As a prominent prisoner, Sirhan was detained in Corcoran State Prison in the north of the country. After telling the authorities several years ago that he would prefer to be housed in a regular prison, he was transferred to the Richard J. Donovan Institution.