High up in the western Himalayas, where China and India meet, soldiers pelted each other with stones and brandished iron rods and sticks at each other at Pangong Lake earlier this month. Dozens were injured, Indian media outlets reported.

There was a similar faceoff in Sikkim, more than 1,000 miles away, a few days later in a patch of border in the eastern part of the Himalayas that had not previously been a flash point.

What prompted the clashes at 14,000 feet — ­where parts of the border are disputed, and it is common for both countries to send patrols up to their respective claim lines and retreat — is unclear.

But the potential for sticks and stones to escalate into something more serious is causing alarm as far away as Washington. And its western border is far from the only place where China is flexing its muscles these days.

Chinese maritime surveillance vessels have confronted a Vietnamese fishing boat and a Malaysian oil exploration ship in the South China Sea in recent weeks, sinking the Vietnamese boat. The Chinese navy sailed an aircraft carrier through the Taiwan Strait twice last month, putting the self-ruled island on alert.

And Beijing this week is set to push through a new national security law for Hong Kong that would essentially strip the city of its remaining autonomy.

The tensions are a reminder “that Chinese aggression is not always just rhetorical,” Alice Wells, a top State Department official on South Asia, said last week.

“Whether it’s on the South China Sea or whether it’s along the border with India, we continue to see provocations and disturbing behavior by China that raises questions about how China seeks to use its growing power,” she told reporters.

The coronavirus pandemic adds another element. A U.S.-
China Economic and Security Review Commission report about Taiwan this month suggested that Beijing was taking advantage of the world being “distracted” by the outbreak.

China is probably more worried about being perceived as weak because of the coronavirus and even more resolved to double down on its sovereignty claims, rather than making brazen moves while the world was looking the other way, said M. Taylor Fravel, director of the security studies program at MIT.

The recent flare-up along the “line of actual control,” which has marked the unofficial border between China and India since they fought a war in 1962, prompted a response from President Trump.

“We have informed both India and China that the United States is ready, willing and able to mediate or arbitrate their now raging border dispute,” he tweeted Wednesday.

Altercations near the line of actual control are not uncommon. India sent its troops in to stop China from building a road in the disputed region of Doklam in 2017, beginning a two-month-long confrontation that triggered fears of war between the nuclear-armed neighbors.

The relationship between the two countries remains tense, exacerbated by efforts from both capitals to stoke nationalist sentiment. The obvious place for this to erupt is at the point where the two countries bump up against each other.

But reports in India suggest China has gone further this time, with troops crossing into territory that India claims in the Galwan River valley, about 125 miles north of Pangong Lake, and setting up camps there.

Analysts said the intrusion in the Galwan valley, if confirmed, represents a break from the past.

“This is seriously uncharted territory,” said Ajai Shukla, an Indian defense analyst and former army officer who has written about the tensions, adding that he could not recall an incident like this in the three decades since India and China established protocols to build confidence at the border. “This is a high-level, coordinated, planned action from the Chinese side.”

Figuring out what is happening in the western Himalayas, where the Indian region of Ladakh faces Tibet, is hampered in no small part by the difficulty of getting access to the region.

“The most benign explanation for this current situation is that this is one of those things that got out of hand,” said Tanvi Madan, an expert on India’s relations with China at the Brookings Institution.

The dispute appears to center on India’s construction of a major road in the Galwan valley that runs roughly parallel to the line of actual control. Both sides object to any development that appears to challenge the status quo.

“China was not happy about this road being completed and inaugurated in October 2019, because it essentially will now allow India to have a stronger presence in that entire area,” Madan said.

Indian media outlets have reported that China’s People’s Liberation Army has deployed almost 5,000 soldiers to territory it claims in the Galwan valley this month.

China “has recently undertaken activities toward hindering India’s normal patrolling patterns,” Anurag Srivastava, a spokesman for India’s Ministry of External Affairs, said last week. “We are deeply committed to maintaining India’s sovereignty and security.”

A spokesman for the Indian Defense Ministry declined to comment on the tensions with China and did not respond to questions about what had occurred in the Galwan valley. Gen. Manoj Naravane, India’s army chief, in remarks to reporters this month played down the incidents as part of an existing pattern of “temporary and short-duration faceoffs” due to the unsettled nature of the frontier.

China’s diplomats also minimized the tensions. Zhao Lijian, a spokesman for the Chinese Ministry of Foreign Affairs, said Wednesday that the two countries “are capable of resolving these issues properly through dialogue and consultation.”

Fueling concerns, China’s aggressive approach on its borders coincides with another big increase in its defense budget, even as its economy grinds almost to a halt amid the pandemic. The Communist Party’s leaders announced a 6.6 percent increase in the defense budget this week, taking annual spending to $178 billion.

While Trump administration officials have criticized China’s actions, the tensions between the United States and China could in fact have led Beijing to stop checking its behavior, said Bonnie Glaser, director of the China Power Project at the Center for Strategic and International Studies.

“For many years, preserving a stable relationship with the U.S. was a top priority for Beijing and may have been a partial restraint on Chinese behavior,” she said.

The tensions over trade, technology and human rights have taken on a new dimension with the emergence of the new coronavirus, which the Trump administration blames China for allowing to spread.

“China now appears to have given up hope of having stable ties with the U.S. under the Trump administration,” Glaser said. “China’s behavior against Hong Kong, pressure on Taiwan and its global disinformation campaign all suggest that Beijing could care less about U.S. reactions to its decisions.”

Fifield reported from Auckland, New Zealand, and Slater reported from New Delhi.