China claimed on Monday that American high altitude balloons had violated its airspace more than ten times since the start of 2022, a claim that was quickly denied by Washington.

The U.S. military fired down what it claims was a Chinese spy balloon on February 4. The balloon’s arrival caused top U.S. diplomat Antony Blinken to postpone a trip to Beijing meant to defuse tensions. China’s charge extended the U.S.-China disagreement.

Since then, the U.S. military has shot down three other flying objects over North America, most recently on Sunday, when an octagonal object was downed over Lake Huron, the Pentagon said.

“Since last year, the U.S.’ high-altitude balloons have undergone more than 10 illegal flights into Chinese airspace without the approval of the relevant Chinese departments,” Chinese foreign ministry spokesperson Wang Wenbin said at a regular briefing in Beijing in response to a question.

Wang did not specifically describe the balloons as military, or for espionage purposes and did not provide further details.

The White House promptly denied China’s accusation, which National Security Council spokeswoman Adrienne Watson dismissed as an effort at damage control by Beijing.

“Any claim that the U.S. government operates surveillance balloons over the PRC (People’s Republic of China) is false,” she said in a statement.

“It is China that has a high altitude surveillance balloon program for intelligence collection, connected to the People’s Liberation Army, that it has used to violate the sovereignty of the United States and over 40 countries across five continents.”

China has failed to offer “any credible explanations” for the intrusions, she added.

Earlier, national security spokesman John Kirby told MSNBC in an interview: “Just absolutely not true. We are not flying balloons over China.”

The U.S. Defense Department did not respond to a request for comment.

China’s assertion comes after the United States shot down what it called a Chinese surveillance balloon off the coast of South Carolina on Feb. 4 after it had drifted across the continental United States for days.

China said the balloon was a civilian research craft that had mistakenly blown off course and accused the United States of overreacting.

Chinese foreign ministry’s Wang said he had no information on the latest three objects shot down by the United States.

Gregory Poling, an Indo-Pacific maritime security expert at Washington’s Center for Strategic and International Studies think tank, said he was not aware of any U.S. use of balloons for surveillance, although he added “I suspect none of us would know for sure.”

He noted that China considers the airspace over Taiwan, over territory it disputes with Japan, and much if not all of the South China Sea to be its territorial air space.