Fireworks exploded over Havana Bay and five Cuban agents imprisoned in the United States sent greetings as ailing leader Fidel Castro turned 81 on Monday, spending his second consecutive birthday convalescing at an unknown location.

From prisons in the United States, five Cuban agents serving long terms on espionage-related charges sent greetings of their own, which were published on Communist party newspaper Granma. Two documentaries about his life will be aired on state television late on Monday night.