In a statement China’s defense ministry said, it had conducted a combat readiness patrol in a direction towards the Taiwan Strait following a visit by a U.S. congressional delegation which arrived on a military aircraft.

In recent months, China has raised the ante in the region with repeated intrusions by its air force on Taiwan.

China has made expanded claims with all of its neighbors including in Vladivostok, Russia, which it does not share a border with. In recent days Chinese belligerence peaked with 4 of its J-16 fighter jets along with two surveillance planes intruding on Taiwan’s air defense zone.

In a statement Taiwanese Premier Su Tseng-chang said, Taiwan-U.S. relations are “very important” and that he respects “mutual visits between friends”. He went on to add, Taiwan will make “appropriate arrangement” based on mutual needs.

The American Institute in Taiwan, the de facto U.S. embassy in the country, did not immediately respond to requests for comments.

In a statement the Pentagon said, it was not uncommon for a congressional delegations to visit Taiwan in a military aircraft.

Pentagon’s spokesman John Kirby did not elaborate on who was on the flight, but said this was the second such congressional trip to Taiwan this year.

“It’s not unusual,” said Kirby.

Like all of China’s neighbors, Taiwan does not recognise Beijing’s claims and said it will defend its freedom and Democracy.

China is not a democracy. China’s parliament, the National People’s Congress, has made a significant change in the country’s constitution removing the two-term limit on the presidency, effectively allowing Xi Jinping to remain President for life. The National People’s Congress is widely seen as a rubber-stamping exercise.