China has accused India of crossing a disputed border between the two countries, as the Indian army said three of its soldiers had been killed in violent clashes.
Tensions flare on a fairly regular basis between the two nuclear-armed neighbours over their 3,500-kilometre border, which has never been properly demarcated.
Just recently thousands of troops were involved in clashes on the frontier in India's Ladakh region, just opposite Tibet.
China's foreign ministry spokesman Zhao Lijian told reporters Indian troops crossed the border twice on Monday, "provoking and attacking Chinese personnel, resulting in a serious physical confrontation between border forces on the two sides".
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Beijing has lodged "strong protests and solemn representations" to Delhi, he said.
The Indian army said there were "casualties on both sides" in Monday's incident on the Himalayan frontier.
"A violent face-off took place yesterday (Monday) night with casualties on both sides. The loss of lives on the Indian side includes an officer and two soldiers," an Indian army spokesman said in a statement.
Last week, China said it had reached a "positive consensus" with India over resolving tensions at the border.
India's Prime Minister Narendra Modi and Chinese leader Xi Jinping have sought to ease the tensions at summits over the past two years when they agreed to boost border communications between their armies.
