China claims sovereignty over democratically governed Taiwan, and says it has jurisdiction over the strait. Taiwan and the United States dispute that, saying the Taiwan Strait is an international waterway.

China's military said on Wednesday it sent fighter jets to monitor and warn a U.S. Navy patrol aircraft that flew over the sensitive Taiwan Strait, a mission that took place just hours after a call between the Chinese and U.S. defence chiefs.

China claims sovereignty over democratically governed Taiwan, and says it has jurisdiction over the strait. Taiwan and the United States dispute that, saying the Taiwan Strait is an international waterway.

The U.S. Navy's 7th Fleet said the P-8A Poseidon maritime patrol and reconnaissance plane, which is also used for anti-submarine missions, flew over the strait in international airspace.

"By operating within the Taiwan Strait in accordance with international law, the United States upholds the navigational rights and freedoms of all nations," it said in a statement. "The aircraft's transit of the Taiwan Strait demonstrates the United States' commitment to a free and open Indo-Pacific."

China's military described the flight as "public hype", adding it had sent fighters to monitor and warn the U.S. plane and "deal with it in accordance with the law and regulations".

"Troops in the theatre are always on high alert and will resolutely defend national sovereignty and security as well as regional peace and stability," the Eastern Theatre Command of the People's Liberation Army said in a statement.

Taiwan's defence ministry said that the U.S. aircraft flew south through the strait and that Taiwanese forces had monitored the situation but observed nothing unusual.

There was no immediate reaction from China.

The last time the U.S. Navy announced a Poseidon had flown through the strait, in December, China's military said it had also sent fighter jets to monitor and warn the aircraft.

The latest Poseidon mission came shortly after U.S. Defense Secretary Lloyd Austin spoke with Chinese Defence Minister Dong Jun, the first engagement the two have had in more than a year as the two countries seek to restore military ties.

Dong told Austin that the Taiwan issue is "core of China's core interests and China's core interests must absolutely not be harmed," according to a readout from his ministry.

"The Chinese People's Liberation Army will never let any Taiwan independence separatist activities and external connivance and support go unchecked," it cited Dong as saying.

The United States is Taiwan's most important international backer and arms supplier despite the absence of formal diplomatic ties, and the issue is a constant irritant for Sino-U.S. relations.