After another incident between Chinese and Philippine vessels in the South China Sea, analysts say there is a risk of a "relatively intense" clash but that neither side wants to escalate the situation.

China's military said it warned off a Philippine warship on Monday after it "illegally entered" waters around Huangyan Island, the Chinese name for Scarborough Shoal, which is also claimed by the Philippines.

A statement from PLA Southern Theatre Command spokesperson Tian Junli said the Philippine vessel had "seriously violated" China's sovereignty.

"The Southern Theatre Command of the Chinese People's Liberation Army organised naval and air forces to track and monitor, issue warnings, and block and manage [the Philippine vessel] in accordance with the law," Tian said, without giving further details.

"The Philippines' actions seriously violated China's sovereignty, seriously violated international law and basic norms of international relations, and could easily lead to misunderstanding and misjudgment."

Tian said China urged the Philippines to "immediately stop infringement and provocation and effectively avoid further escalation of the situation".

"Troops in the theatre remain on high alert at all times and resolutely safeguard national sovereignty, [as well as] security, peace and stability in the South China Sea," Tian said.

Manila's national security adviser Eduardo Ano said the Philippine ship - a PS39 Pohang-class corvette - had been on a "routine patrol" in the general vicinity of the island under international law "without any untoward incident".

"It did not illegally enter any space under Chinese sovereignty ... Chinese vessels, as usual, conducted a shadowing movement of PS39," he said.

"China is again overhyping this incident and creating unnecessary tensions between our two nations.

"Nonetheless, the Armed Forces of the Philippines and Philippine coastguard will not be deterred by the aggressive and illegal activities of People's Liberation Army Navy/China coastguard/militia in the West Philippine Sea," Ano said.

The Chinese coastguard took similar action against a Philippine gunboat near Scarborough Shoal on October 10.

On October 22, the Philippines said Chinese vessels had collided with two of its ships near Second Thomas Shoal, which is also claimed by both countries. China said it had taken "necessary measures" to safeguard its sovereignty and that these were carried out "professionally and with restraint".

The encounters are part of an increasing atmosphere of confrontation between Beijing and Manila in the contested waters, which has coincided with intensified China-US rivalry in the Indo-Pacific.

Chen Xiangmao, an associate research fellow with the National Institute for South China Sea Studies in Hainan province, said the involvement of a Philippine corvette - rather than a coastguard ship - in the latest incident could raise fears that Manila was seeking to "recapture Huangyan Island by force".

Increasing pressure from the Philippines and "irrational action" could lead to a "relatively intense" military conflict between the two sides, according to Chen.

He said the recent increase in confrontations near contested islands could be due to the US defence assurance given to the Philippines, which "may feel that China may not take measures against it".

"China will indeed not make such a decision in the short term, given its international reputation, diplomatic pressure and the potential for a conflict with the United States, which could be involved," he said.

Washington and Manila agreed in May that their 1951 Mutual Defence Treaty would cover the South China Sea. After this month's collisions at Second Thomas Shoal, US President Joe Biden reaffirmed the commitment to defend the Philippines if it is attacked by the PLA in the South China Sea.

Collin Koh, a maritime affairs expert at the S. Rajaratnam School of International Studies, Nanyang Technological University in Singapore, said it was likely that Chinese warships were involved in Monday's incident since the statement came from the PLA rather than the coastguard.

Koh said despite the presence of warships, he did not believe either side wanted to escalate the situation.

"But whether you're talking about coastguard, maritime militia or you talk about navies, there is always the attendant risk of an accidental or inadvertent clash because of miscalculation, misjudgment," he said.

The Philippine strategy is to increase its presence around disputed islands in a bid to normalise its operations and push China to consider a "new status quo", according to Koh.

"All these actions are meant to gradually change or give the impression that, you know, the Filipinos are ... still in the picture," he said. "And therefore, going forward, Beijing has to take that into account."