China has accused the United States and Britain of undermining peace and stability in the Taiwan Strait with their decision to send warships through the waterway, a mission that the two allies described as routine.

The People’s Liberation Army Eastern Theatre Command said Chinese naval and air forces closely monitored thedestroyer USS Higgins and the British frigate HMS Richmond as they transited the strait on Friday.

The passage amounted to “harassment and provocation”, command spokesman Senior Colonel Shi Yi said, adding that the action “sent wrong signals and undermined peace and stability in the Taiwan Strait”.

“The command remains on high alert and is committed to safeguarding national sovereignty and ensuring regional peace and stability,” he said.

A week ago, the Canadian frigate HMCS Ville de Quebec and the Australian guided-missile destroyer HMAS Brisbane also sailed through the strait, prompting a similar warning from Beijing.

China’s third and mostadvanced aircraft carrier, the Fujian, also passed through the strait, with Beijing announcing early on Friday that the vessel was on its way to conduct scientific research and training exercises in the South China Sea.