LOS ANGELES (AP) _ Police say they arrested a man they believe committed 18 bank robberies in the San Fernando Valley northwest of downtown Los Angeles in the past two months.

Harold H. Ghaemmaghami, 33, of Reseda was arrested Friday by police and FBI agents as he drove through Van Nuys, authorities said.

He was being held for investigation of bank robbery at Parker Center Jail, said Sgt. Robert Minich.

Ghaemmaghami is believed to be the ''Tall Man,'' so named because he was described as well over 6 feet tall, who hit 18 banks, the latest this week, said Detective Joe Getherall.