China has said it is "seriously dissatisfied" over a visit by India's prime minister to a disputed border region that was at the centre of a brief war between the two countries more than 40 years ago.
Manmohan Singh, the Indian prime minister, visited the Himalayan state of Arunchal Pradesh on October 3, on what officials said was a campaign tour ahead of state elections.
For its part India has defended Singh's visit, expressing "disappointment and concern" at China's criticism and reiterating that Arunchal Pradesh is "an integral and inalienable part of India".
Singh himself made no comment on China or the border dispute during his visit.
But in China's first comments on the visit on Tuesday, the foreign ministry in Beijing warned it could undermine improving relations between the two countries.
"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," spokesman Ma Zhaoxu said in a statement on the ministry's website.
Beijing claims all of Arunachal Pradesh – an area of some 90,000 km square – as part of what it regards as "southern' Tibet.
|Despite warming ties, territorial disputes remain between India and China [EPA]
Countering those claims, India says China is occupying 38,000 km square of its territory in the Himalayas.
The two sides fought a brief but bloody war in 1962, after Chinese forces launched a cross-border incursion into Indian-held territory.
The fighting ended after China declared a unilateral ceasefire, although a formal agreement ending the conflict was never signed and the disputed territorial claims remain unresolved.
More recently relations between the China and India have warmed and trade between the two has flourished, with China now India's second-largest trade partner.
In 1996 the two sides signed a pact to maintain "tranquility" along their shared border, agreeing to hold regular border resolution talks, the most recent of which took place in August.