A Tibetan man living in New Zealand says his community is being spied on and harassed for protesting against China's law on promoting ethnic unity and progress.

The man, Gaden, told RNZ he knew of a few incidents where people had faced pressure from Chinese nationals.

"They don't come ... straight to us, they just take the photo from a distance," he said.

He did not know if they would attempt to take any further action, but said "to be honest, as a Tibetan, I don't care".

In its latest threat assessment, the SIS said diaspora community groups living in this country were being unfairly targeted by foreign states and proxies seeking to limit their democratic rights and freedoms.

"In Tibet, you cannot hoist a Tibetan national flag. However, we do still have the prayer flags in front of the monastery, or people's house or anywhere. Now, they have started to take it down, burn it down, stamp it on it," he said.

Some Tibetans were setting themselves on fire in response to the law, he said, with one such incident occuring in July in front of United Nations headquarters in New York, US.

"He burned himself for the just cause of Tibetans, because we are all very frustrated," Gaden said.

"We are very peaceful people. We don't want to take up or cause any harm inside of China. We just need our own identity preserved."

The Chinese Embassy has been approached for comment.