Netherlands ? A court convicted four Dutch Muslims on Friday of plotting terrorist attacks and sentenced them to up to eight years in prison, a victory for prosecutors who had failed several times before to convict would-be terrorists before they acted.

The heaviest sentence was reserved for Samir Azzouz, 20. Judges said he had played a “central role” in the group and had prepared a suicide video meant to “strike terrible fear into the Dutch people.”

The group had allegedly planned to attack Dutch politicians, including Prime Minister Jan Peter Balkenende, and the headquarters of the Dutch intelligence agency.

Azzouz had been arrested twice before as part of investigations into alleged terrorist activities. The first time he had bomb-making materials, but was released without charge on a technicality. The second time he was charged with planning an attack but was acquitted when the judges found the preparations had not advanced far enough to prove a terrorist conspiracy.