A bomber attached to an aviation regiment of the air force under the PLA Southern Theater Command taxies on the runway to get ready for a flight training exercise in late February, 2023. (Photo:China Military Online)

A US warship was expelled again from Chinese territorial waters off the Xisha Islands in the South China Sea by the Chinese People's Liberation Army (PLA) when it attempted to trespass for a second consecutive day on Friday.

Calling the US move an escalated provocation, Chinese experts said the PLA should remain on high vigilance.

Without authorization from the Chinese government, US guided missile destroyer the USS Milius on Friday illegally entered Chinese territorial waters off the Xisha Islands again, sabotaging the peace and stability in the South China Sea, Senior Colonel Tan Kefei, a spokesperson at China's Ministry of National Defense, said in a press release on Friday.

The PLA Southern Theater Command tracked, monitored and warned away the US warship in accordance with the law, Tan said.

The US military's move seriously violated China's sovereignty and security, severely infringed on international law, and is yet another piece of ironclad proof of US navigational hegemony and "militarization" buildup in the South China Sea, said the spokesperson.

"We sternly demand that the US side immediately stop this kind of provocative action, or it will bear the serious consequences caused by them," Tan said, noting that the PLA will take all necessary measures to resolutely safeguard national sovereignty and security, and firmly maintain peace and stability in the South China Sea.

Friday's incident marks the second consecutive day the US naval vessel was expelled from the Chinese waters in the South China Sea.

On Thursday, the USS Milius was warned away by PLA naval and air forces when it made an illegal intrusion into the Chinese territorial waters off the Xisha Islands, Senior Colonel Tian Junli, a spokesperson at the PLA Southern Theater Command, said in a press release on that day.

It also marks an upgrade in China's response, as Thursday's incident was dealt with by the PLA Southern Theater Command, and Friday's incident was announced by the Defense Ministry, observers said.

It is rare for a US warship to trespass into the same region of Chinese territorial waters twice in a short period of time, a Chinese military expert who requested anonymity told the Global Times on Friday.

This is an escalated provocation from the US as it tries to deny China its sovereignty and stir up trouble in the South China Sea, the expert said. 

As a country from outside the region, the US does not want countries around the South China Sea to have any fruitful talks, as tensions in the region benefit the US' plan of containing China but harm all other countries' interests, analysts said.

Chinese military expert Song Zhongping also warned of US threats from a tactical point of view. He told the Global Times that the US close-in reconnaissance attempt could be a preparation from the US military for a possible future conflict, so the PLA must also be prepared.

The Philippines has agreed to make four additional military bases available for US use, which could lead to increased US reconnaissance activities on China, which the PLA should take corresponding countermeasures against, Song said.