TAIPEI (Reuters) – Taiwan scrambled jets and navy ships on Wednesday as a group of Chinese warships, led by its sole aircraft carrier, sailed through the Taiwan Strait, the latest sign of heightened tension between Beijing and the self-ruled island.

China’s Soviet-built Liaoning aircraft carrier, returning from exercises in the South China Sea, was not encroaching in Taiwan’s territorial waters but entered its air defense identification zone in the southwest, Taiwan’s defense ministry said.

As a result, Taiwan scrambled jets and navy ships to “surveil and control” the passage of the Chinese ships north through the body of water separating Taiwan and China, Taiwan defense ministry spokesman Chen Chung-chi said.

Taiwan military aircraft and ships have been deployed to follow the carrier group, which is sailing up the west side of the median line of the strait, he said.

Taiwan’s top policymaker for China affairs urged Beijing to resume dialogue, after official communication channels were suspended by Beijing from June.

“I want to emphasize our government has sufficient capability to protect our national security. It’s not necessary to overly panic,” said Chang Hsiao-yueh, minister for Taiwan’s Mainland Affairs Council, during a news briefing in response to reporters’ questions on the Liaoning.

“On the other hand, any threats would not benefit cross-Strait ties,” she said.

China has said the Liaoning was on an exercise to test weapons and equipment in the disputed South China Sea and its movements complied with international law.

On the weekend, a Chinese bomber flew around the Spratly Islands in a show of “strategic force”, a U.S. official said on Tuesday.

The latest Chinese exercises have unnerved Beijing’s neighbors, especially Taiwan which Beijing claims as its own, given long-running territorial disputes in the South China Sea.

Chinese Vice Foreign Minister Liu Zhenmin said China’s ships “couldn’t always remain in port” and the navy had to hone its capabilities.

“The Taiwan Strait is an international waterway shared between the mainland and Taiwan. So, it is normal for the Liaoning to go back and forth through the Taiwan Strait in the course of training, and it won’t have any impact on cross-Strait relations,” Liu said at a briefing on Asia-Pacific security.

China claims most of the energy-rich waters of the South China Sea, through which about $5 trillion in ship-borne trade passes every year. Neighbors Brunei, Malaysia, the Philippines, Taiwan and Vietnam also have claims.

China distrusts Taiwan President Tsai Ing-wen and has stepped up pressure on her after U.S. President-elect Donald Trump broke years of diplomatic protocol and took a congratulatory call last month from her.

Trump then riled China by casting doubt on the “one China” policy that Beijing regards as the basis of U.S.-Chinese relations.

Tsai drew anger from China again when she met senior U.S. Republican lawmakers in Houston on Sunday en route to Central America, in a transit stop that Beijing had asked the United States to not allow.

Beijing suspects Tsai wants to push for the island’s formal independence, a red line for the mainland, which has never renounced the use of force to bring what it deems a renegade province under its control.

Tsai says she wants to maintain peace with China.

(Reporting by J.R. Wu and Faith Hung; Additional reporting by Michael Martina in Beijing; Editing by Michael Perry, Robert Birsel)