JAKARTA, March 13 (Reuters) - Authorities in Indonesia's popular holiday island of Bali have asked the central immigration agency to cancel a visa-on-arrival policy for Russian and Ukrainian nationals after tourists were found working illegally. Bali Governor I Wayan Koster said on Sunday he has asked the Ministry of Law and Human Rights to tighten visa requirements by cancelling the visa-on-arrival facility specifically for Russian and Ukrainian citizens due to a series of violations. See here for a complete list of exchanges and delays