In a report the navy said critical errors by the pilot and an officer on the ground had caused the bomb to hit the wrong target.

The death of the civilian security guard David Sanes Rodriguez sparked calls across Puerto Rico for the withdrawal of the US Navy from the island of Vieques off the coast of Puerto Rico.

Vieques has been used as a practice range for the last five decades.

War games: Vieques has been used since WW II

Navy officials said "two critical" human errors were two blame for the death of Mr Sanes on 19 April.

"Essentially what you had here is two people who made critical mistakes. You have the pilot inadvertently sighting the wrong target to bomb. And a person on the ground who allowed him to do it," said Capt. Jim Stark, commanding officer of the Roosevelt Roads Naval Station.

'Confused by clouds'

According to the report, the jet involved in the accident took off from the USS John F Kennedy aircraft carrier together with another plane for a practice bombing run.

Navy officials said "scattered cloud cover" apparently confused the pilot so that he erroneously sighted a navy observation post on Vieques as the intended target.

A range control officer on the ground made visual contact with only one of the planes, assumed both were still flying together when he gave the pilot of the second plane the okay to fire.

But the second plane was off target.

None of the soldiers involved have been identified, the navy says only that the pilot has been banned from flying and faces disciplinary proceedings.

The range control officer was taken off firing range duties and faces further action.

A critical time

The navy report comes at a time of increased campaigning for a return of Vieques to local control.

Puerto Ricans took their protest to the navy

The island is part of Puerto Rico, a US commonwealth in the Caribbean, but two-thirds of it is under navy control.

Public outrage increased when it was revealed last month that the navy had used napalm during training exercises on Vieques.

The navy argues says its training facilities there are essential to national defence.

'Violation of human rights'

Last month, about 50,000 Puerto Ricans spent America's Independence Day protesting against the use of Vieques for target practice.

The march, which saw pro-US politicians and independence activists united, followed the release last week of a report by the special committee on Vieques, a bipartisan group appointed by Governor Pedro Rossello.

The report accused the US Navy of having violated basic human rights by its continued bombing of Vieques.