Beijing is intensifying its warnings to Indian troops to get out of a contested region high in the Himalayas where China, India and Bhutan meet, saying China has been restrained but "restraint has its limits."

India says its troops entered the area in the Doklam Plateau in June after its ally Bhutan complained a Chinese military construction party was building a road inside Bhutan's territory.

Beijing says the dispute has nothing to do with India, and has demanded that Indian troops withdraw unilaterally before any talks can be held on the matter.

This week, the foreign and defence ministries, as well as the ruling Communist Party's mouthpiece, reiterated that China will not back down.

Chinese defence ministry spokesman Ren Guoqiang said late Thursday that while Chinese armed forces had shown "utmost goodwill" and a "high level of restraint ... restraint has its limits."

"No country should underestimate the Chinese forces' confidence and capability to safeguard peace and their resolve and willpower to defend national sovereignty, security and development interests," Ren said in a statement.

China and Bhutan have been holding talks over their border dispute since the 1980s and Bhutan feared the road construction would affect the process of drawing their boundary. India said its troops were attempting to urge the Chinese forces not to change "the status quo" and that any construction would have "serious security implications for India."

Some Indian experts say that by building the road, China may be able to gain access to a narrow strip of Indian land known as the Siliguri Corridor or Chicken's Neck. If China was able to block the corridor, it would isolate India's northeast from the rest of the country.

On Wednesday, China's Foreign Ministry issued a document setting out what it called "the facts" about Indian troops "trespassing" into Chinese territory, calling on India to immediately and unconditionally withdraw and saying Beijing would work with Bhutan to resolve the boundary issue.

The document says that as of the end of July, more than 40 Indian border troops remained, down from when more than 270 Indian troops with weapons and two bulldozers advanced more than 100 metres into Chinese territory on June 16.

In editorials this week, the official People's Daily said Indian officials and media had "concocted all kinds of groundless excuses" for the incursion.