"China's position on the China-India boundary question is consistent and clear-cut," said Chinese foreign ministry spokesperson Geng Shuang in response to reports that PM Modi visited Arunachal Pradesh today.
"The Chinese government has never recognised the so-called Arunachal Pradesh and is firmly opposed to the Indian leader's visit to the disputed area," Mr Geng was quoted as saying by state-run Xinhua news agency.
"We will lodge stern representations with the Indian side," he said.
Mr Geng said that China and India had reached important consensus on properly managing disputes, and the two sides were working to resolve the territorial disputes through negotiation and consultation.
"The Chinese side urges the Indian side to honour its commitment and abide by the relevant consensus, and refrain from taking any action that may complicate the boundary question," Mr Geng said.
He urged India to cherish the hard-won momentum of improvements in bilateral relations and create enabling conditions for the boundary talks and the development of bilateral relations.
China routinely protest visits of Indian leaders to Arunachal Pradesh and reiterates its claims over it.