Pyotr Masherov, 62, a World War II guerrilla leader who rose to become head of the Byelorussian Communist Party organization and an alternate member of the Soviet Politoburo, died Saturday in an auto accident.

His death was announced Sunday by Tass, the official Soviet News agency. The announcement gave no details of the accident.

Mr. Masherov had been near the upper ranks of power in the Soviet Union for 15 years and had long been tipped as a potential successor to ailing Premier Alexei Kosygin. Western diplomats who met him described Mr. Masherov as "urbane and intelligent."

He had been first secretary of the Communist Party organization in the Soviet republic of Byelorussia -- the third-largest republican party organization -- since 1965 and one of nine alternate members of the Politburo since 1966.

Born in the Byelorussian village of Shirki, Mr. Masherov was a physics and mathematics teacher until the outbreak of World War II. He became a guerrilla leader under Nazi occupation, and was awarded the title of "Hero of the Soviet Union" for his partisan exploits. After the war, he rose through the ranks of the Young Communist League and then the Communist Party.

The dispatch by Tass made no mention of survivors.