A SENIOR mainland official yesterday warned that the ultimate solution to the problem of Vietnamese refugees fleeing China was to repatriate them to Vietnam. Refugee official Xu Liugen said the Vietnamese - most of whom were ethnic Chinese and had lived in China for more than 12 years - should be sent home ''in accordance with international practice''. He was commenting on the position of the 2,400 Vietnamese who have arrived in Hong Kong from China over the past few months. Only 109 have been sent back to the mainland. Mr Xu did not made clear whether his remarks applied only to those Vietnamese who had fled to Hong Kong or all those living on the mainland. Most of the Vietnamese living in China fled there in the late 1970s during the boat people crisis. China accepted them as refugees because most of them were ethnic Chinese. They were allowed to settle in China and many live in Guangxi province. Beijing had not raised the issue of repatriation with the Vietnamese Government, but it should be dealt with through diplomatic channels, said Mr Xu, the director of the Department of International Co-operation Office for Indochina Refugees Affairs underthe Civil Affairs Ministry. Hong Kong was last night quick to distance itself from Mr Xu's remarks. Acting Refugee Co-ordinator Eddy Chan Yuk-tak said: ''It's quite clearly China's own affair, which has nothing to do with the Hong Kong Government. It sounds like a matter for the UNHCR [United Nations High Commissioner for Refugees] to comment on, rather than the Hong Kong Government.'' He refused to comment on the legality of sending home anyone granted refugee status in China. As far as Hong Kong was concerned, the ex-China Vietnamese migrants who flooded here this summer were illegal immigrants and would be sent back. China said it would take back the migrants once their identities had been confirmed. Legislative Council security panel convenor Elsie Tu welcomed Mr Xu's comments. But she did not think the move, even if made, would solve the problem once and for all. ''I think it hinges very much on whether Vietnam treats those people properly,'' Mrs Tu said. However, United Democrat James To Kun-sun did not think the proposal would help ease the pressure of Vietnamese refugees on Hong Kong. He said the Vietnamese had come to Hong Kong ''because they were ill-treated in China''. If China could improve its way of handling Vietnamese refugees, the problem could be satisfactorily solved, he said. Mr Xu said that China would take back all the Vietnamese over the next few months. About 26 of the illegal immigrants are due to be taken to the border at dawn on Wednesday to be handed over to Chinese officials in the second repatriation to Guangdong. A much more difficult operation, however, will be the forced return of the majority of migrants, who fled to Hong Kong from outside Guangdong in the summer exodus. The Government has yet to find a ship both safe and secure enough to take hundreds of Vietnamese at once to their homes on Hainan Island, Guangxi and Yunnan. According to Mr Xu, the third batch of several hundreds will be deported next month by sea, first to Hainan and then to Guangxi. This month's repatriation went smoothly, with the first batch of 109 migrants sent back to the Yin Xiong tea farm in Guangdong's Yin De county, he said. Measures were being taken to curb the influx of Vietnamese migrants to Hong Kong. Mr Xu did not divulge details, but noted that there had been no new arrivals of migrants in Hong Kong recently.