TAIPEI (Reuters) - Three U.S. Air Force planes, including two B-52 bombers, flew near Taiwan on Wednesday, the island’s defense ministry said, after Taiwan’s air force scrambled earlier in the week to intercept Chinese jets.

FILE PHOTO: Incumbent Taiwan President Tsai Ing-wen and Vice President-elect William Lai attend a rally after their election victory, outside the Democratic Progressive Party (DPP) headquarters in Taipei, Taiwan January 11, 2020. REUTERS/Tyrone Siu/File Photo

The United States is Taiwan’s most important international backer, even in the absence of formal diplomatic ties, and is also the island’s main source of arms.

Tensions spiked between Taiwan and China, which claims the island as its own, on Sunday and Monday, as Taiwan sent F-16s to shadow approaching Chinese bombers and fighters.

Taiwan’s Defense Ministry said one U.S. MC-130, a special mission aircraft based on the C-130 Hercules transport aircraft, flew down the Taiwan Strait in a southerly direction on Wednesday.

The two U.S. B-52 bombers skirted Taiwan’s east coast, also in a southerly direction, the ministry added.

The U.S. Air Force has a major base on the southern Japanese island of Okinawa, which is near Taiwan.

Speaking in Singapore, a senior U.S. State Department official, Clarke Cooper, referred to the Chinese flights and told CNBC it was “completely inappropriate of China to take such an aggressive act.”

“That aggressive act is not just a reflection on China’s relationship with Taiwan, it certainly is reflective about how China may be looking at the entire region in total,” said Cooper, the assistant secretary for political-military affairs.

On Tuesday, a State Department spokeswoman said China should “immediately cease its coercive efforts” and resume dialogue with Taipei.

China has described its exercises on Sunday and Monday as actions to guard national sovereignty.

It has been flying what it calls “island encirclement” drills since 2016 when Taiwan President Tsai Ing-wen first took office. Beijing believes Tsai, who won re-election last month, wishes to push the island’s formal independence.

Tsai says Taiwan is an independent country called the Republic of China, its official name.

Taiwan has urged China to focus its efforts on fighting the new coronavirus rather than menacing the island.

Taiwan Foreign Ministry spokeswoman Joanne Ou said in a statement earlier on Wednesday that China’s military activities had only caused anger on the island and harmed the peaceful development of relations across the strait.

“Our government will continue to adopt a pragmatic and restrained stance, prudently handle cross-strait relations, and deepen cooperation with countries with similar ideals, including the United States, in response to the rising Chinese military threat,” she added.