China’s accusation widened a dispute with the US that began last weekend after the US military shot down what it says was a Chinese spy balloon, prompting top US diplomat Antony Blinken to cancel a trip to Beijing designed to ease tensions.

“Since last year, the US’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 US 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 programme for intelligence collection, connected to the People’s Liberation Army, that it has used to violate the sovereignty of the US and over 40 countries across five continents,” Watson added.

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

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

The US defence department did not respond to a request for comment.

Kirby separately said the White House still did not know what three other flying objects downed since Friday were, but that the administration would release more details as soon as the debris is captured and analysed.

China’s assertion comes after the US 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 US for days.

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

In recent days, the US 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.

Wang said he had no information on the latest three objects shot down by the US.