People voted on Sunday in a mayoral election in the Okinawan city that is home to a US airbase whose planned move has set Tokyo and Okinawa at odds, with the central government giving strong backing to the incumbent.

Prime Minister Shinzo Abe's government has dangled prospects of a bigger budget for Okinawa, backing for a Disney resort and promises of aid for impoverished children in Japan's second-poorest prefecture to boost the current mayor's chances.

Defeat would boost resistance to moving the Futenma base to the less populated Henoko area of the island, as agreed with key ally the United States two decades ago.