Taiwan Coast Guard said on Sunday it has deployed vessels to respond to a Chinese operation in waters east of the island.
The fresh escalation came after Chinese state media reported on Saturday that the “law enforcement operation” responded to talks between Japan and the Philippines to draw a boundary in the affected waters.
Taiwan reported that a Chinese survey vessel had joined a coast guard ship in waters around Pratas Island — administered by Taiwan — on Saturday in the northern part of the South China Sea.
Taipei said it was "the first observed instance of Chinese coast guard and survey vessels acting in coordination to provoke Taiwan".
Taipei, on Sunday, described the Chinese move as a “violation of international law.”
China, which asserts Taiwan is part of its territory, called the talks "illegal" and has claimed exclusive control over the waters.
The Chinese ships have been monitored "throughout the entire process" and Taiwan "has deployed the necessary vessels to respond appropriately," the Taiwanese coast guard said in a statement.
Taiwan said it had detected four Chinese government vessels departing from Xiamen port, which had sailed outside Taiwanese restricted waters southwest of the island.
Taiwan's coast guard dispatched more than five vessels "to assist with surveillance".
The Chinese vessels were expected to arrive "in the relevant waters" on Sunday, the statement said, adding that "China does not enjoy any sovereign rights in the waters east of Taiwan".
Tokyo and Manila said last month they would start formal talks "to delimit the maritime boundary" of an economic zone and continental shelf between them, angering Beijing.
On Saturday, China's transport ministry organised maritime police from coastal provinces Fujian and Guangdong to "conduct a special maritime traffic law enforcement operation in waters east of Taiwan Island", state news agency Xinhua said.
The report did not give details on the operation, including how long it lasted or whether it was still ongoing, and it did not say whether maritime police dispatched ships to the area.
The operation was "a necessary action taken against Japan and the Philippines' unilateral announcement that they would start 'negotiations on delimiting a maritime boundary'" near Taiwan, Xinhua added.
Taiwan said on Wednesday it should be consulted on the Japan-Philippines talks.
Manila and Tokyo's shared grievances over Chinese maritime territorial claims have seen them draw increasingly close in recent years.
Japan and China are in territorial and economic disputes in the East China Sea, where coast guard ships from both sides routinely stage tense stand-offs.
Beijing has meanwhile deployed navy and coast guard vessels in the South China Sea in a bid to bar the Philippines from strategically important reefs and islands, leading to a string of confrontations.
