Both sides pledged to safeguard their territory and also to try to end a standoff that has dramatically raised the stakes between the nuclear-armed Asian giants, reports AP.

Twenty Indian troops were reportedly killed in the clashes on Monday night in the Ladakh region's Galwan Valley, while it was not clear whether China suffered any casualties.

Indian security forces said neither side fired any shots, with some officials saying the soldiers were carrying anti-riot gear rather than weapons. The Indian soldiers, including a colonel, died of severe injuries suffered in sub-zero temperatures after the two sides threw rocks and traded blows, Indian officials said.

It was the deadliest conflict between the sides in 45 years, and escalated a standoff in the disputed region that began in early May, when Indian officials said Chinese soldiers crossed the boundary at three points, setting up tents and guard posts and ignoring verbal warnings to leave.

That triggered shouting matches, stone-throwing and fistfights, much of it replayed on television news channels and social media.

Chinese Foreign Minister Wang Yi warned New Delhi not to underestimate Beijing's determination to safeguard what it considers its sovereign territory. His comments came in a phone call Wednesday with his Indian counterpart, Subrahmanyam Jaishankar.

Wang said China demanded that India conduct a thorough investigation and "harshly punish" those responsible.

"The Indian side would best not make an incorrect judgement of the situation, would best not underestimate China's strong determination to safety its sovereign territory," Wang said in a statement issued by the foreign ministry.

He repeated China's claims that India was solely responsible for the conflict, saying Indian forces had crossed the Line of Actual Control that divides the thousands of troops from both sides deployed in the area.

Jaishankar, in turn, accused China of erecting a structure in the Galwan Valley, which he called a "premeditated and planned action that was directly responsible for the resulting violence and casualties," according to a statement.

He added that the incident would have "serious repercussions" on India's relationship with China, but that both sides were committed to further disengaging on the remote plateau of the Himalayan terrain.

‘Watershed moment in India-China ties’

Indian Prime Minister Narendra Modi hailed the soldiers killed in the clashes.

"Their sacrifices won't go to waste," he said. "For us, the unity and sovereignty of the country is the most important thing. India wants peace, but when provoked, it is capable of giving a fitting reply, be it any kind of situation."

While experts said the two nations were unlikely to head to war, they also believe easing tensions quickly will be difficult.

"This will likely be a watershed moment in India-China relations and the geopolitics of the Indo-Pacific," said Abraham Denmark, Asia programme director at The Wilson Center. "Both countries are led by men who have embraced nationalism, and both countries are facing tremendous domestic and international upheaval as a result of COVID-19 and other long-standing problems."

The main questions now are if either side can find a path to deescalation and whether India's allies such as the US will help.

"It is a highly volatile and dangerous situation between two nationalistic, nuclear powers at a time when American influence has badly diminished," Denmark said.

China claims about 90,000 square kilometers (35,000 square miles) of territory in India's northeast, while India says China occupies 38,000 square kilometers (15,000 square miles) of its territory in the Aksai Chin Plateau in the Himalayas, a contiguous part of the Ladakh region.

India unilaterally declared Ladakh a federal territory while separating it from disputed Kashmir in August 2019. China was among the handful of countries to strongly condemn the move, raising it at international forums including the UN Security Council.

Thousands of soldiers on both sides have faced off over a month along a remote stretch of the 3,380-kilometer (2,100-mile) Line of Actual Control, the border established following a war between India and China in 1962 that resulted in an uneasy truce.

The United Nations urged both sides "to exercise maximum restraint."

"We are concerned about reports of violence and deaths at the Line of Actual Control between India and China," UN associate spokesperson Eri Kaneko said. "We take positive note of reports that the two countries have engaged to de-escalate the situation."

Also read: 20 soldiers killed in clash with Chinese troops, India claim