BEIJING (AP) — China said it closely monitored the flight of a U.S. surveillance plane through the Taiwan Strait on Monday, accusing the U.S. of having “deliberately disrupted and undermined the regional situation.”

Chinese forces organized to keep an eye on the passage of the P-8A Poseidon anti-submarine patrol plane and “all matters were in hand,” the People’s Liberation Army’s Eastern Theater Command said in a social media posting.

China regards self-ruled Taiwan as its own territory to be brought under its control by force if necessary, and views the passage of foreign military ships and aircraft through the 160-kilometer (100-mile)-wide strait as deliberate snubs and provocations.

While U.S. warships regularly transit the strait, one of the world’s busiest shipping lanes, it is more rare for U.S. military aircraft to do so.

The PLA command accused the U.S. of having “played up” the flight, which it said “endangered peace and stability in the Taiwan Strait.”

“We firmly oppose this. Theater troops maintain a high level of alert at all times and will resolutely defend national sovereignty and territorial integrity," it said.

In a brief statement, the U.S. 7th Fleet said a Navy P-8A Poseidon transited the Taiwan Strait in international airspace on Monday.

“The United States will continue to fly, sail, and operate anywhere international law allows including within the Taiwan Strait," it said. “By operating within the Taiwan Strait in accordance with international law, the United States upholds the navigational rights and freedoms of all nations."

The flight comes as tensions between the sides have spiked over the shooting down of a suspected Chinese spy balloon off the East Coast and U.S. warnings to Beijing not to provide Russia with military aid to help its war against Ukraine.

China regularly sends warships into waters near Taiwan and fighters and other military aircraft into its air defense buffer zone in an attempt to intimidate the island's pro-independence government and its U.S. supporters.