A suburban Maryland banker was kidnaped at knifepoint on his way to work yesterday and driven around Prince George's County for much of the day by two men who threatened to kill him unless his bank paid ransom.

The banker eventually fled his captors unharmed. No ransom was collected, at least in part, authorities said, because the abductor's instructions were too vague to follow.

The FBI said it was unclear whether the extortion scheme was planned in advance or developed spontaneously in the course of what was to be a robbery. And officials said they were not sure if the victim actually escaped or was casually released. Two suspects were arrested last night.

The FBI gave this acount:

Events began about 10 a.m. near the Landover Mall branch of the Suburban Trust Co. As Charles A. Kimmey, the branch manager, left his car and walked toward his office, he was confronted by a man with a knife who forced him back to the car and they drove off.

After a while, the car stopped for a second man and the two men began to go through Kimmey's personal papers, which showed him to be a bank official.

Subsequently, the bank was contacted by someone who threatened to kill the manager unless ransom was paid. Authorities said a large ransom was asked, but they declined to specify a figure.

The bank tried twice to deliver the money. One attempt was made in a heavily wooded area near a creek. Nobody came for it, the FBI said. The second attempt was made in an industrial park near another wooded area. The money was not picked up that time either.

However, after his abductors arrived at what they considered the second pickup point and left the car, Kimmey fled. One of the abductors took the car keys with him, but Kimmey knew where a second set was hidden. He used them to drive away.

Some confusion still surrounded the abductors' intentions. "We're not sure if the guy escaped or if he was released," said Edward Hegarty, chief of the FBI's Baltimore office.

Two brothers from District Heights were arrested last night and charged with extortion in the incident. They were identified as Richard Jerome Kit, 20, of 1914 Rochelle Ave., and Theodore Kit, 22, of 1938 Rochelle Ave.