(CNN)At least 20 Indian soldiers have died after a "violent face-off" with Chinese troops along the countries' de facto border in the Himalayas late Monday, the Indian army has said.
The incident occurred during a "deescalation process" underway in the Galwan Valley in the disputed Aksai Chin-Ladakh area, where a large troop build-up has reportedly been taking place for weeks now on both sides of the border, before senior military commanders began talks earlier this month.
The Indian army had earlier said three soldiers had died, but added on Tuesday that a further 17 troops "who were critically injured in the line of duty at the standoff location and exposed to sub-zero temperatures in the high altitude terrain have succumbed to their injuries."
The deaths are the first military casualties along the two countries' disputed border for more than 40 years.
According to the earlier Indian army statement, there was loss of life "on both sides," but it did not specify any number of Chinese casualties.
Senior military officials from both sides are currently meeting to defuse the situation, the statement added.
"India and China have been discussing through military and diplomatic channels the de-escalation of the situation in the border area in Eastern Ladakh," said India's External Affairs Ministry spokesman Anurag Srivastava on Tuesday.
He said senior commanders had "agreed on a process for such de-escalation" during a "productive meeting" on Saturday, June 6, and ground commanders had met regarding the implementation.
"While it was our expectation that this would unfold smoothly, the Chinese side departed from the consensus to respect the Line of Actual Control (LAC) in the Galwan Valley," he said in the statement.
"Both sides suffered casualties that could have been avoided had the agreement at the higher level been scrupulously followed by the Chinese side," he added.
"Given its responsible approach to border management, India is very clear that all its activities are always within the Indian side of the LAC. We expect the same of the Chinese side. We remain firmly convinced of the need for the maintenance of peace and tranquility in the border areas and the resolution of differences through dialogue. At the same time, we are also strongly committed to ensuring India's sovereignty and territorial integrity."
Indian Defense Minister Rajnath Singh met with the External Affairs Minister, the Chief of Defense Staff, and the chiefs of the Army, Navy and Air Force and to review the "operational situation in Eastern Ladakh" earlier on Tuesday, the army said.
At a regular news conference Tuesday, Chinese Foreign Ministry spokesman Zhao Lijian said that on Monday, "Indian troops seriously violated our consensus and twice crossed the border line for illegal activities and provoked and attacked Chinese personnel which lead to serious physical conflict between the two sides."
"China has lodged strong protest and representation with the India side, and we once again we solemnly ask the India side to follow our consensus and strictly regulate its front line troops and do not cross the line and do not stir up troubles or take unilateral moves that may complicate matters," Zhao added.
"We both agreed to resolve this issue through dialogue and consolation and make efforts for easing the situation and upholding peace and tranquility in the border area."
Zhao did not comment on whether there had been any Chinese casualties.
China's People's Liberation Army (PLA) released a statement Tuesday night calling on the Indian army to immediately stop what it described as "provocative actions" and to "resolve the issue through the correct track of dialogue and talks."
"The sovereignty of the Galwan Valley region has always belonged to China," Zhang Shuili, the spokesman of the Western Theater said in a statement on China's Ministry of Defense website. "Indian troops violated its commitment, crossed the borderline for illegal activities and deliberately launched provocative attacks."
Zhang added that the "serious physical conflict between the two sides" had "resulted in casualties."
An Indian military banner post is seen next to a road in Ladakh in 2012. The region shares a border with both China and Pakistan.
"We solemnly ask the India side to strictly regulate its front line troops, immediately stop all infringement and provocative actions, go toward the same direction with China, and return to the correct track of dialogue and talks to resolve differences," the statement read.
Monday's deaths are the first military casualties along the disputed border for more than four decades, Indian defense experts told CNN.
"We have not had casualties on the Line of Actual Control for at least 45 years," said Happymon Jacob, an associate professor and political analyst at New Delhi's Jawaharlal Nehru University. "This is perhaps a game-changer. This is perhaps the beginning of the end of the rapport that India has enjoyed with China for 45 years."
Former Indian Chief of Army Staff, General Bikram Singh, also confirmed to CNN this is the first such deadly incident in the last 45 years.
Tensions have been growing in the Himalayas along one of the world's longest land borders since last month, with New Delhi and Beijing both accusing the other of overstepping the LAC that separates the two nuclear armed neighbors. The territory has long been disputed, erupting into numerous minor conflicts and diplomatic spats since a bloody war between the two countries in 1962.
The LAC runs between Chinese-controlled Aksai Chin and the rest of the disputed Jammu and Kashmir region.
The rough border line was the result of the India China border dispute in 1962, but neither side agrees exactly where it is or how long it is.
Aksai Chin is administered by China as part of Xinjiang, but is also claimed by the Indian government as part of Ladakh.
The reported troop build up had left many worried about the potential for a confrontation, particularly as both Chinese and Indian media have published jingoistic calls for action.
Both Chinese President Xi Jinping and Indian Prime Minister Narendra Modi have built public support in large part on nationalism and a promise of future greatness. This often translates into aggressive rhetoric, particularly when playing to a domestic audience.
Such an approach was evidenced in Chinese coverage of the PLA maneuvers in the Himalayas. Equally, despite Delhi's public calls for easing tensions, leading Indian government figures have struck an aggressive tone, with Home Affairs Minister Amit Shah telling a rally of the ruling Bharatiya Janata Party (BJP) earlier this month that "any intrusion into the the borders of India will be punished."
"Some used to say that US and Israel were the only countries which were willing and capable of avenging every drop of the blood of their soldiers," Shah said. "(Modi) has added India to that list.''
Writing for CNN this month, retired Indian general Singh said that part of the problem is that the de facto border, the LAC, is so ill defined.
"At strategic and operational levels, both militaries have exercised restraint," he said. "However, at the tactical level, face-offs occur due to differing perceptions of where the actual border is as the LAC is not delineated on the ground. While face-offs get resolved locally, those related to the building of infrastructure, such as roads and defence fortifications, invariably take longer and require a combination of military and diplomatic initiatives."
Speaking before the most recent clash, former Indian Foreign Secretary Nirupama Rao said she hoped the current crisis won't lead to an abandonment of long-standing diplomatic negotiations over the disputed territory.
"Even if tensions rise and tempers fray, they would do well to remember that they have to continue to manage their differences in a grown-up way because armed clashes and military combat can have extremely serious repercussions for the stability of the region going beyond the ambit of the purely bilateral relationship between the two countries," she said.
