Incantations ring out at Mongolia's largest monastery as worshippers pray alongside pictures of the Dalai Lama, whose 90th birthday on Sunday has raised fresh questions about the future of the 600-year-old Tibetan spiritual institution.

The Dalai Lama says he'll have a successor, after all, ending years of speculation that he might be the last person to hold the role and meaning he'd be reincarnated.

For much of the past century, the Dalai Lama has been the living embodiment of Tibet’s struggle for greater freedoms under Chinese Communist Party rule, sustaining the cause from exile even as an increasingly powerful Beijing has become ever more assertive in suppressing it.