India's opposition leader Narendra Modi, favourite to win this year's polls, on Saturday warned neighbour China to shed its "expansionist mindset" as he toured a disputed region in the remote northeast.

Modi, the prime ministerial candidate of the Hindu nationalist Bharatiya Janata Party (BJP), said China should instead focus on forging peaceful bilateral ties with India.

Modi was speaking during an election rally in the state of Arunachal Pradesh nestled in the eastern stretch of the Himalayas that China claims as its own.

"The world has changed. An expansionist mindset will not be accepted. China will also have to do away with such a mindset," Modi said in comments posted on his official website.

"Arunachal Pradesh is an integral part of India and will always remain so. No power can snatch it away from us."

China and India share a de facto border, known as the Line of Actual Control (LAC), which has never been formally demarcated.

The unresolved border dispute has soured bilateral relations which are often prickly and marked by mutual distrust -- the legacy of a brief, bloody border war in 1962 over Arunachal Pradesh.

The border dispute flared again last April, with India accusing Chinese troops of intruding deep into Indian-held territory, sparking a three-week stand-off that was only resolved when troops from both sides pulled back.

The countries have since signed accords and held meetings to maintain peace on the border.

Modi's latest attack on China is likely to ruffle feathers in the neighbouring country, which has also been criticised for its aggressive claim to almost all of the South China Sea.

Modi is tipped to be elected as India's prime minister, with his party leading rival Congress in opinion polls ahead of general elections due by May.