BEIJING (AP) — China on Monday accused the U.S. of indiscriminate use of force when the American military shot down a suspected Chinese spy balloon Saturday.

The U.S. shot down a balloon off the Carolina coast after it traversed sensitive military sites across North America. China insisted the flyover was an accident involving a civilian aircraft.

Vice Foreign Minister Xie Feng said he lodged a formal complain with the U.S. Embassy on Sunday over the “U.S. attack on a Chinese civilian unmanned airship by military force.”

The presence of the balloon in the skies above the U.S. dealt a severe blow to already strained U.S.-Chinese relations that have been in a downward spiral for years. It prompted Secretary of State Antony Blinken to abruptly cancel a high-stakes Beijing trip aimed at easing tensions.

Xie repeated China’s insistence that the balloon was a Chinese civil unmanned airship that blew into U.S. mistake, calling it “an accidental incident caused by force majeure.”

China would “resolutely safeguard the legitimate rights and interests of Chinese companies, resolutely safeguard China’s interests and dignity and reserve the right to make further necessary responses," he said.