A Christian has been sworn in as governor of Indonesia's capital for the first time in in 50 years despite protests from Islamic hardliners who insist the job should be reserved for a Muslim.

Basuki Tjahaja Purnama, also the first ethnic Chinese person to become an Indonesian governor, takes the oath of office Wednesday in a ceremony led by President Joko "Jokowi" Widodo at the state palace.

Widodo was governor until becoming president in August. Purnama had served as his deputy.

Purnama has a reputation for outspokenness and has a track record of combating graft and cutting red tape.

His installment as head of the city of 12 million people comes despite frequent street protests by Islamist groups, who say a Muslim should get the job.