Media playback is unsupported on your device Media caption The Dalai Lama speaks exclusively to the BBC about his worries for Tibetan monks and nuns

The Tibetan spiritual leader, the Dalai Lama, says he is very worried about the growing number of monks and nuns setting themselves on fire to protest against Chinese rule in Tibet.

He told the BBC he was not encouraging such actions - saying there was no doubt they required courage, but questioning how effective they were.

There have been 11 cases of self-immolation so far this year.

Most have resulted in death - the latest a 35-year-old nun two weeks ago.

The BBC has obtained graphic footage of the moment she set herself alight, prompting horrified cries from onlookers. Later, Chinese security forces flooded the area.

The shocking video footage was smuggled across the border to India and shown to the BBC.

Tibetan monks and nuns are using self-immolation as the latest tactic in their struggle against 60 years of Chinese rule, says the BBC's Andrew North.

But it is a sensitive issue for the man they are dying for - the Dalai Lama, the Tibetan spiritual leader.

'How much effect?'

In an interview with our correspondent, he said he was not encouraging his followers to sacrifice themselves - as alleged by China.

"The question is how much effect" the self-immolations have, the Dalai Lama said.

"That's the question. There is courage - very strong courage. But how much effect?

"Courage alone is no substitute. You must utilise your wisdom."

Asked whether he feared the actions could make life worse for people in Tibet, he said: "Many Tibetans sacrifice their lives.

"Nobody knows how many people killed and tortured - I mean death through torture. Nobody knows.

"But a lot of people suffer. But how much effect? The Chinese respond harder."

China has condemned the self-immolation campaign as immoral and inhuman, saying it will never succeed.

The growing number of monks and nuns prepared to set themselves on fire is a sign of increasing desperation in Tibet, our correspondent says.

They know while the West has backed the Arab Spring, with China it talks with a much quieter voice, he says.

That leaves Tibetans with few options to shine a light on their struggle.

From inside Tibet, the word is that more monks are preparing to make the ultimate sacrifice, our correspondent adds.