China on Wednesday warned the United States against interfering in its domestic affairs after Washington expressed "serious concern" over a spate of self-immolations by Tibetan monks.

"The Chinese government attaches great importance to and safeguards the various basic rights of ethnic groups, including their freedom of religious belief," foreign ministry spokesman Liu Weimin told reporters.

"We firmly oppose making use of religious affairs to interfere in China's domestic affairs," he said in response to a question about Washington's concerns.

State media reported Monday that a Tibetan monk died after self-immolating in the northwestern province of Qinghai, taking to 15 the number of people who have set themselves on fire in Tibetan areas in less than a year.

It was the first time the Tibetan-inhabited province had been hit by such a death. Most self-immolations have taken place in neighbouring Sichuan province, in what rights groups say are protests against perceived religious repression.

The incident came after two former monks in Sichuan set themselves on fire on Friday -- one died and another is being treated in hospital.

"We're seriously concerned by reports that three more Tibetans have self-immolated over the past few days," State Department spokeswoman Victoria Nuland said Monday.

"These actions clearly represent... enormous anger, enormous frustration with regard to the severe restrictions on human rights, including religious freedom, inside China."

The exiled Dalai Lama has condemned self-immolations, which many Buddhists believe is contrary to their faith, but said recently Tibetans faced "cultural genocide" under hardline Chinese rule that he blamed for the protests.

But China says it has raised the standard of living for many Tibetans, pointing to huge ongoing investment poured into Tibetan areas.

Nuland said the US had also "urged the Chinese government... to loosen up in Tibet and allow journalists and diplomats and other observers to report accurately, and to respect the human rights of all of their citizens."

"And we have called the Chinese government policies counterproductive," she added.

Liu countered that China administered "religious affairs in accordance with laws so as to maintain religious order."

"The constant occurrence of self-immolations in Tibet regions does not meet the aspirations of Tibetan people for realising a peaceful life," he said.