NEW DELHI — Tensions along the India-China border took an alarming turn on Tuesday after Chinese and Indian officials accused each other’s soldiers of firing warning shots, apparently the first time in decades that guns had been aggressively used along the disputed frontier.
Military activities along the unofficial border, which zigs and zags through some of the highest mountain ranges on Earth, are difficult to verify.
But according to a statement from the Chinese military, Indian troops on Monday “took the outrageous step of firing warning shots” near a Chinese border patrol. India’s actions, the Chinese said, were “a grave military provocation of a vile character.”
Indian officials, however, denied their soldiers had fired any shots and said it was the Chinese who broke the long tradition of refraining from using firearms, a protocol in place for decades.
Chinese soldiers “fired a few rounds in the air in an attempt to intimidate” Indian troops, the Indian military said in a statement. “Despite the grave provocation,” the statement said, Indian troops “exercised great restraint and behaved in a mature and responsible manner.”
One thing is clear: The dispute that has been building on the Himalayan border that separates the two nuclear-armed powers is only sharpening as their broader relationship steadily deteriorates.
In June, a huge brawl broke out high in the mountains and Chinese troops beat to death 20 Indian soldiers.
In August, a soldier belonging to a secretive force of Tibetan refugees who work with the Indian army died after he stepped on a land mine. The Chinese authorities have not revealed the extent of their casualties.
Both sides have rushed in tens of thousands of reinforcements, backed by artillery, tanks and fighter jets. In India, the clashes have sparked a wave of nationalism and further turned the public against China, with street protests and boycotts of Chinese-made goods.
For years, the more than 2,000-mile-long unmarked border between the countries has been a sore spot. In 1962, the two countries fought a war over it. China won, wrenching away a huge but sparsely populated plateau from India.
After that, small skirmishes erupted from time to time until the 1970s, when relations between India and China began to improve. That led to a protocol in which both sides ordered their border patrols to refrain from firing their weapons during disputes, which tend to be frequent. Because the border is unmarked and both countries patrol some of the same areas, the troops often find themselves face to face with each other.
Indian officers called the use of firearms, even as a warning, a “game changer.”
Indian military analysts said the situation was heading into a dangerous stalemate. Neither side wants to start a war. But neither side wants to back down either.
“Bite by bite, China has been eating away at Indian borderlands,” said Brahma Chellaney, a professor of strategic studies at the Centre for Policy Research in India’s capital, New Delhi.
The Chinese government increasingly seems unwilling to negotiate in many of the disputes it finds itself in, from the claims it has made in the South China Sea to its trade wars with the United States. When it comes to India, Chinese officials and those aligned to them in the Chinese news media often take a condescending and belligerent tone.
“China is several times stronger than India, and India is no match for China,” read a recent editorial in The Global Times, an organ of the Communist Party. “We must smash any Indian illusion that it can deal with China by colluding with other powers, such as the U.S.”
On Monday, the Chinese government took another dig at India.
When asked about reports that have been circulating in the Indian news media that five Indians from the border state of Arunachal Pradesh may have been kidnapped by Chinese forces, Zhao Lijian, a spokesman for China’s Foreign Ministry, said he did not have any information.
But, Mr. Zhao emphasized, “the Chinese government has never recognized the so-called ‘Arunachal Pradesh.’”
Hari Kumar contributed reporting from New Delhi; Sameer Yasir from Srinagar, Kashmir; Chris Buckley from Sydney, Australia, Claire Fu from Beijing and Steven Lee Myers from Seoul, South Korea.