Modi paid a low-key visit to the northeast Indian state of Arunachal Pradesh on Thursday, where he inaugurated a local convention centre, but the trip was quickly criticised by China, which also claims the area.
“The Chinese government has never recognized the so-called Arunachal Pradesh and is firmly opposed to the Indian leader’s visit to the disputed area,” said Chinese Foreign Ministry spokesperson Geng Shuang.
“We will lodge stern representations with the Indian side.”
Last year, hundreds of Chinese and Indian troops faced off on the Doklam plateau, a small strip close to the intersection between China, India and Bhutan.
The border dispute began in mid-June after Chinese troops started building a road on the Himalayan plateau.
India has an army base nearby and moved soldiers into the flashpoint zone to halt the work, prompting Beijing to accuse it of trespassing on Chinese territory.
The two nations finally pulled back their troops in mid-August, averting a full-blown crisis.