TAIPEI: Taiwan said on Monday its armed forces have the right to self-defence and counterattack amid "harassment and threats", in an apparent warning to China, which last week sent numerous jets across the mid-line of the sensitive Taiwan Strait.

Tensions have sharply spiked in recent months between Taipei and Beijing, which claims democratically-run Taiwan as its own territory, to be taken by force if needed.

Chinese aircraft crossed the mid-line to enter the island's air defence identification zone on Friday and Saturday, prompting Taiwan to scramble jets to intercept them, and President Tsai Ing-wen to call China a threat to the region.

Taiwan's defence ministry said it had "clearly defined" procedures for a first response amid "high frequency of harassment and threats from the enemy's warships and aircraft this year".

It said Taiwan had the right to "self-defence and to counterattack" and followed the guideline of "no escalation of conflict and no triggering incidents".

Taiwan would not provoke, but it was also "not afraid of the enemy", it added.

MID-LINE "DOES NOT EXIST"

Taiwanese and Chinese combat aircraft normally observe the mid-line of the Taiwan Strait and do not cross it, although there is no official agreement between Taipei and Beijing on doing so, and the rule is observed unofficially.

"Taiwan is an inseparable part of Chinese territory," Foreign Ministry spokesman Wang Wenbin told reporters in Beijing. "The so-called mid-line of the Strait does not exist."

Since 2016 Taiwan has reported only five Chinese incursions across the line, including the two last week.

Late on Monday, Taiwan's Defence Ministry reported two Chinese anti-submarine aircraft had flown into Taiwan's air defence identification zone - but not over the mid-line - to the island's southwest, and were warned away by Taiwanese fighters.

The drills came as Beijing expressed anger at the visit of a senior US official to Taipei.

US Secretary of State Mike Pompeo on Friday accused Beijing of bluster when asked about the Chinese activity.

A senior Trump administration official on Monday said the Chinese aircraft movements were "consistent with past Chinese behavior" during heightened tensions and appeared more a reaction to Taiwan domestic politics. The official, speaking on condition of anonymity, said Washington did not believe China was seeking to escalate into a military confrontation.

On Monday, the official China Daily newspaper said the United States was trying to use Taiwan to contain China but nobody should underestimate its determination to assert its sovereignty over the island.

"The US administration should not be blinkered in its desperation to contain the peaceful rise of China and indulge in the US addiction to its hegemony," it said in an editorial.

China has been angered by stepped-up US support for Taiwan, including two visits by top officials, one in August by Health Secretary Alex Azar and the other last week by Keith Krach, undersecretary of state for economic affairs.

The United States, which has no diplomatic ties with the island but is its strongest backer, also plans new arms sales to Taiwan.