BIRMINGHAM, Ala. -- A former Ku Klux Klansman convicted in a 1963 church bombing that killed four black girls claimed in a letter from prison that the FBI was behind the crime.

Much of Bobby Frank Cherry's letter, delivered this week to The Associated Press, was copied from a story by an alternative magazine, Media Bypass.

The magazine reported claims that a former U.S. marshal from Birmingham maintained for years that the bombing was instigated by FBI agents and government informants to gain sympathy for civil rights legislation.

The marshal, Dan Moore, based his belief on a telephone call he received from a supervisor several hours before the bombing warning of riots or demonstrations the following week, Cherry's letter said. Moore died last year at 77.

The prosecutor in the bombing case dismissed Cherry's claims.

"It's ludicrous," Doug Jones, a former U.S. attorney now in private practice, said Friday.