A US army base worker has been jailed for life for rape and murder in Okinawa, in a case that sparked anti-US protests in Japan.

Kenneth Franklin Shinzato was found guilty of assaulting and killing a 20-year-old local woman last year.

The incident prompted deep outrage among locals and renewed calls for US bases to be removed entirely.

The US maintains thousands of troops on Okinawa on several bases, and locals have long objected to their presence.

Shinzato was a former US Marine who worked as a civilian contractor at the Kadena air base in Okinawa. He was accused of attacking and killing Rina Shimabukuro in April 2016.

He admitted to charges of rape resulting in death and abandoning her body, but denied he had intended to murder her.

Prosecutors said he had repeatedly hit his victim on the head and stabbed her in the neck during the attack.