Two practitioners of Falun Gong on a trip to Tonga were allegedly questioned by Tongan immigration officials, after the Chinese embassy there expressed extreme concern about their visit.

Shelley Shao and Yuan Li travelled to Tonga late last month to teach locals about the Chinese spiritual movement Falun Gong and say they were questioned by local immigration officials during their stay.

One of the women involved, Shelley Shao says a Chinese businessman gave the women a warning the day after an interview on a Tongan television station.

"He said you should be careful because the Chinese embassy also know you are here and they said they want to take some action to your guys, and I said 'What kind of action?' and he said, 'I'm not sure because I don't want to [be] involved in this kind of things, but you should be very careful," she said.

Radio Australia has obtained a document from the Chinese embassy telling Tonga's Ministry of Foreign Affairs they are "extremely concerned" that the women might hold what they called "an anti-China gathering" during their visit.

The embassy asks Tonga to take "immediate and appropriate actions...to avoid possible harm" to the long-standing friendship between the countries.

Another document signed by Tonga's Secretary for Foreign Affairs instructs the Prime Minister's Office, police and defense officials to avoid "compromising Tonga's good relations with China".

Derek Brien, the Deputy Executive Director of the Pacific Institute of Public Policy, says the case is a sign of China's changing role in the Pacific.

"It is an example of why we should all be mindful of what a rising influence of China in the Pacific region may involve in terms of the political dynamics and the changing political dynamics," he said.