China on Friday angrily rejected US charges that its policies in Tibet were leading Tibetans to set themselves alight in protest and accused Washington of backing independence forces in the Himalayan region.

More than 90 Tibetans have set themselves on fire since 2009 to protest China's rule of the Tibetan plateau, rights groups have said, with the frequency of incidents increasing sharply in November.

On Wednesday, US Special Coordinator for Tibetan Issues Maria Otero expressed concern over the burnings and called on China to let Tibetans "express their grievances freely".

The United States "is deeply concerned and saddened by the continuing violence" in Tibet, the State Department said.

Official Chinese rhetoric "that denigrates the Tibetan language, the Dalai Lama, and those who have self-immolated has further exacerbated tensions", Otero said in a statement.

China's foreign ministry spokesman on Friday reacted angrily to the comments, calling them "interference in China's internal affairs".

"The relevant statement by the US official did not criticise the Tibetan splittist activity of the Dalai Lama group and Tibet independence forces, but instead criticises and blames the Chinese government policies," Hong Lei said.

"The Chinese side has expressed strong dissatisfaction and firm opposition as well as stern representations with the US side."

Washington also urged Beijing to talk with the Dalai Lama "without preconditions" and to allow journalists, diplomats "and other observers unrestricted access to China's Tibetan areas".

But Hong reiterated Beijing's long-held position that the Dalai Lama, the Tibetan spiritual leader, was inciting the burnings as a means of realising Tibetan independence, but did not offer any proof of such actions.

The Dalai Lama has lived in exile in India since 1959, when he fled an abortive uprising against Chinese rule in Tibet.