The Dalai Lama has slammed censorship in China as "immoral", following accusations that the Chinese government blocked him from traveling to South Africa to celebrate Desmond Tutu's 80th birthday.

The Tibetan spiritual leader spoke with Tutu on Saturday, answering questions via a video link, instead of attending an event to honour the South African anti-apartheid activist a day after his birthday.

His absence was symbolised by an empty chair at the event at the University of the Western Cape where he was meant to deliver an inaugural peace lecture.

Al Jazeera's Gerald Tan reports.