China has strongly criticised a visit by Indian Prime Minister Manmohan Singh to the disputed north-east Indian state of Arunachal Pradesh.
The Chinese foreign ministry accused Mr Singh of ignoring Beijing's concerns.
China claims large areas of Arunachal Pradesh which lies on the Himalayan border it shares with India. Delhi said the remarks "do not help" border talks.
Analysts say China is angry over a trip planned by exiled Tibetan leader the Dalai Lama to the state in November.
Mr Singh visited Arunachal Pradesh earlier this month ahead of state assembly polls which were held on Tuesday. In January 2008 he made the first prime ministerial visit to the mountainous state in more than 10 years.
China and India fought a brief border war in 1962 - partly over Arunachal Pradesh - and the frontier has yet to be settled despite several rounds of talks.
"We demand the Indian side address China's serious concerns and not trigger disturbances in the disputed region so as to facilitate the healthy development of China-India relations," Chinese foreign ministry spokesman Ma Zhaoxu said in a statement posted on the ministry's web site.
The Indian foreign ministry responded by saying that Arunachal Pradesh is an "integral and inalienable part of India".
It said that China's criticisms "did not help the process of ongoing negotiations between the two governments on the boundary question".
Beijing claims 90,000 sq km of land that comprises Arunachal Pradesh which it sees as "southern" Tibet.
It has also expressed displeasure over a planned visit by the Dalai Lama to the state's Tawang monastery in November.
"The Chinese don't want the Dalai Lama to visit Arunachal Pradesh at any cost," Nanigopal Mahanta, who teaches politics at Guwahati university, told the BBC's Subir Bhaumik.
Much of China's territorial claims in the Himalayas are based on areas Tibet controlled before it was taken over by the Chinese.
"So if a Tibetan leader like the Dalai Lama visits Arunachal Pradesh and says the whole state is part of India and was never part of Tibet, that takes the wind out of the Chinese claims," Mr Mahanta said.
Our correspondent says that when India and China enjoyed better relations, especially in the late 1990s, Delhi did not allow the Dalai Lama to visit Arunachal Pradesh or any area contested by China.
The Chinese reciprocated by opening border trade on the Nathu La pass after 40 years - a move many in India saw as recognition of Indian control over Sikkim.
But our correspondent says that changed after India started developing the "strategic relationship" with the US, which raised fears of encirclement in the Chinese security establishment.
Trade between China and India has flourished in recent years, but several border disputes - including over Kashmir and Sikkim - have never been resolved.
China remains India's largest trading partner, with two-way trade volumes crossing $50bn in 2008.
Mistrust between Delhi and Beijing has recently gained momentum with reports in the Indian media of Chinese incursions along the border.
There were also protests by a member of India's governing Congress party earlier this month after the Chinese embassy issued different visas to residents of Indian-administered Kashmir.