China said on Friday it had lodged an official protest against Prime Minister Narendra Modi's visit to a border region claimed by both countries.
China disputes the entire territory of Arunachal Pradesh, calling it south Tibet. Its historic town Tawang, a key site for Tibetan Buddhism, was briefly occupied by Chinese forces during a 1962 war.
"The Chinese government has never recognized the so-called 'Arunachal Pradesh'," a statement on the Chinese Foreign Ministry's website said on Friday.
It said Modi's visit was "not conducive to the overall development of bilateral relations".
Modi visited Arunachal Pradesh on Friday to inaugurate the opening of a train line and power station. He did not mention China but pledged billions of dollars of investment to develop infrastructure in the region.
"I assure you that you will witness more development in the state in the next five years than it has seen in the last 28 years," Modi said, addressing a huge crowd.
Faster transport links and exploitation of Arunachal Pradesh's hydro-electric potential are the keys to fighting poverty and bringing about rapid development in the frontier state, he said.
In January, China objected to statements by Japan's foreign ministry supporting India's claim to the region.
A visit by U.S. President Barack Obama to India in January was widely seen as a sign Modi is moving closer to the United States, to offset rising Chinese influence in Asia and, in particular, intensifying activity by the Chinese navy in the Indian Ocean.
