The admission was picked up by the American news network, CNN, in a message to a website which has been used in the past by al Qaeda to claim responsibility for attacks, including the synagogue fire in Tunisia in which mainly German tourists died and strikes on two ships in Yemen.
In a separate development, police in Indonesia say a man currently being questioned about the blast has admitted he was involved with those responsible for the attack.
Indonesia's national police chief, General Da'i Bachtiar, identified the man as Amrozi. General Bachtiar told reporters Amrozi was on the resort island at the time of the attacks.
He is the first suspect named over the three blasts that rocked Bali. The car-bomb was by far the biggest of the blasts, destroying the Sari nightclub and killing mainly foreign tourists.
