Beijing, China - Beijing accused the United States on Monday of having flown more than 10 illegal balloons over China in the past year, in a diplomatic spat triggered by the detection and downing of a suspected Chinese surveillance balloon in US airspace.

"The US should first reflect upon itself and change course, instead of smearing other countries and inciting confrontation," Foreign Ministry spokesperson Wang Wenbin told the media in Beijing.

"It is also quite common for US high altitude balloons to enter into other countries," he said.

Washington also sent "aircraft and warships" to gather information on China, the spokesperson noted, adding that this year 64 sorties had been recorded in the South China Sea.

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China claims a large part of the disputed sea area. The international arbitration court in The Hague rejected the claims in 2016. Despite the ruling, Beijing is building military installations there.

"It's quite clear to the global community which country is the number one spy empire in the world," Wang said, referring also to US surveillance activities and its large spy network.

The US had monitored calls and chat messages by the leaders of European countries including Germany, France, Norway, Sweden, and the Netherlands, the spokesperson said.

He reiterated that the Chinese balloon that entered US airspace last week was "an entirely unexpected isolated event caused by force majeure" and said he did "not have any information" on any of the other unidentified unmanned objects detected over the country.

Washington has now shot down an overall four unmanned objects, officials said on Sunday, with the latest being downed over Lake Huron on the order of US President Joe Biden.