Robert F Kennedy Jr is convinced that a lone gunman was not solely responsible for the assassination of his uncle, president John F Kennedy, and said his father believed the Warren Commission report was a "shoddy piece of workmanship", Belfast Telegraph reported.

Mr Kennedy and his sister, Rory, were interviewed in front of an audience in Dallas as a year of observances begins for the 50th anniversary of the president's death.

Their uncle was killed on November 22, 1963. Five years later, their father was assassinated in a Los Angeles hotel during his primary victory celebration.

Robert Kennedy said his father believed the Warren Commission, which concluded Lee Harvey Oswald acted alone in killing the president, was a "shoddy piece of workmanship". He said that he, too, questioned the report.

"The evidence at this point is convincing that it wasn't a lone gunman," he said, but he did not say what he believed may have happened.