A prison officer was killed today by a bomb planted in the car he was driving in Belfast, police said. The bomb exploded as the officer was driving through predominantly Protestant east Belfast, said the Royal Ulster Constabulary, the province's police force. The victim was not immediately identified, but police said he was a prison officer in his mid-40s. Police said children from a nearby elementary school were walking home for lunch when the bomb exploded nearby, but escaped injury. There was no immediate claim of responsibility for the bombing. Prison officers are among the targets of the Irish Republican Army in its campaign to rid Northern Ireland of British rule and unite it with the Irish Republic. It was the 81st killing in the province this year, and brought the official death toll since Northern Ireland's present strife erupted in 1969 to 2,699.