LUEBECK, Germany (AP) _ Extreme rightist Kay Diesner was convicted of murder and two counts of attempted murder Monday, and sentenced to life imprisonment in what is believed to be the first neo-Nazi slaying of a German police officer.

Diesner, 25, belonged to no organized neo-Nazi group at the time of his February shooting spree, and his case increased fears that extreme rightists were going deeper underground.

Police said Diesner confessed to shooting a bookstore owner Feb. 19 and then opening fire on two policemen at a highway rest stop Feb. 23. Officer Stephen Grage was killed.

Diesner claimed he was acting in self-defense.

Although Diesner apparently acted alone, he had been close to neo-Nazi leader Arnulf Priem, whose National Alternative group was banned in 1992. He also had ties to the White Aryan Resistance, which has links to groups in Sweden and the United States.