NEW DELHI - The Indian army said on Tuesday (June 16) that 20 of its soldiers were killed in clashes with Chinese troops at a disputed border site, in a major escalation of a weeks-long standoff in the western Himalayas.

The statement comes as India and China held marathon military talks on Tuesday to prevent a border row from intensifying and destabilising bilateral ties, after the deaths of an Indian colonel and two junior soldiers in the Ladakh region.

This is the worst border tension between the two countries in nearly 45 years.

There was no official confirmation of how many were killed or injured on the Chinese side after a violent clash, involving stones and batons, broke out between Chinese and Indian troops in the Galwan Valley on Monday night.

India and China have disputes along several points of the Line of Actual Control (LAC), the de-facto border, and the latest flare-up occurred even as troops were disengaging in the Galwan Valley, one of at least four points where a troop build-up took place last month. Both armies had moved soldiers and military equipment to the region. The two countries remained engaged diplomatically.

High-level military talks were held throughout the day to defuse tensions in the Galwan Valley.

Ministry of External Affairs official spokesman Anurag Srivastava said senior commanders on June 6 had agreed on a de-escalation and were implementing it when the "Chinese side departed from the consensus to respect the LAC in the Galwan Valley", resulting in a "violent face-off".

India dismissed China's accusation of Indian transgressions in Chinese territory, and said Indian activities were within the Indian side of the LAC.

Mr Srivastava said: "We remain firmly convinced of the need for the maintenance of peace and tranquillity 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."

The sudden flare-up comes as both countries had emphasised the need to resolve the border dispute peacefully.

India and China, which went to war in 1962, have disputes along several areas of their nearly 4,000km-long border, which is poorly demarcated in many areas.

Still, unlike India's border with Pakistan, there has been no cross-border firing along the China-India border in over five decades.

The last shot fired along the LAC was in 1967 in a clash in Sikkim territory, while the last Indian fatalities along the border happened in 1975 when four Indian soldiers were killed in the north-eastern state of Arunachal Pradesh.

On Tuesday, Chinese Foreign Ministry spokesman Zhao Lijian told reporters that Indian troops provoked and attacked Chinese personnel after crossing the border twice on Monday.

The spokesman said: "Indian troops seriously violated our consensus and twice crossed the border line for illegal activities and provoked and attacked Chinese personnel, which led to serious physical conflict between the two sides, and China has lodged strong protest and representation with the Indian side."

While there was no official word on casualties on the Chinese side, the Global Times newspaper editor-in-chief Hu Xijin tweeted that the "Chinese side also suffered casualties in the Galwan Valley physical clash".

The Global Times is the mouthpiece of China's ruling Communist Party.

India, in earlier talks with China to resolve the situation, had been demanding both sides withdraw to positions before the confrontation started last month, when Chinese patrols moved into areas at Pangong Tso Lake and the Galwan Valley region, which both countries claim are part of their territory.

The current stand-off has also intensified calls within India for the government to present a clear picture of what is happening along the border with China.

Critics have accused the Indian government of underplaying its border troubles with China, while the opposition has asked the government to take it into confidence given the seriousness of the situation.

Within the Indian government, there were multiple rounds of meetings.

Analysts said the border troubles with China were clearly far more serious than visualised.