The Dalai Lama on Saturday slamed censorship in China as "immoral" and poked fun at denunciations of himself in a video chat with Desmond Tutu after he was not granted a visa in time to travel to South Africa.

The exiled Tibetan spiritual leader's 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 to wrap Tutu's 80th birthday celebrations.

"Some Chinese officials describe me as a demon so naturally some fear about the demon," the Dalai Lama told Tutu via a laughter-filled live video link when asked why the Chinese feared him.

"First I'm hurt... (Now) I feel laughing, so I immediately respond yes I have horn," he added, miming horns on his head with his fingers.

The furore over the visa overshadowed the run-up to Tutu's birthday with the former anti-apartheid activist launching a virulent attack on President Jacob Zuma's administration for kowtowing to its biggest trade partner China.

The Dalai Lama said hypocrisy and telling lies had unfortunately become part of life in "the communist totalitarian system" and people who spoke truthfully and honestly sparked discomfort.

"I often tell him (Tutu) 1.3 billion Chinese people should have every right to know ... reality, then 1.3 billion Chinese people also have the ability to judge what's right, what wrong, so therefore censorship is immoral."

He also urged China to raise its judicial system up to international law standards.

China clearly had the potential to take "a constructive role" in the world, he said.

"Respect, trust from the rest of the world is very necessary. For that reason, transparency is very essential," he added.

The discussion between the two Nobel Peace Prize laureates who are close friends was filled with banter, after a last ditch attempt by Tutu's office urging the government to grant the Dalai Lama a visa failed.

"As a man of truth, man of God, please live long," the Dalai Lama told Tutu.

"Your 90th birthday, I'm looking forward. At that time, don't forget send me (an) invitation. Then we can test your government."

In turn, Tutu admitted to a "mutual admiration society" and praised the Tibetan as a person who "makes holiness so attractive" and "a bundle of joy" despite being in exile for more than 50 years.

"He is in fact quite mischievous. I have to warn him sometimes and say 'hey, hey, hey, look here, the cameras are on us, you need to try and behave like a holy man'," he said.

China has always sought to curb the Dalai Lama's overseas travels, warning host governments that any visit would harm ties, especially if he is met by state officials.

The Tibetan has lived in India since 1959 since fleeing an abortive uprising against Chinese rule.

Describing the previous century as a century of violence, he urged talk to solve problems and urged compassion.

"This century should be (the) century of dialogue," he said.

The talk wrapped a three-day celebration for Tutu which included a book launch of a new biography and a church service in the cathedral where he fought the white minority regime.