Important sensors and electronics parts are among the "significant" debris recovered from a suspected Chinese surveillance balloon shot down over the Atlantic earlier this month, according to the US military.

"Crews have been able to recover significant debris from the site, including all of the priority sensor and electronics pieces identified as well as large sections of the structure," the US Northern Command said in a statement on Monday.

China insists the balloon, which spent several days flying over North America, was an errant weather observation aircraft with no military purpose, but the United States says it was a sophisticated high-altitude spying vehicle that is part of a program with global reach.

A US F-22 Raptor fighter jet shot it down off the coast of South Carolina on Feb 4, and teams have since been working to recover the debris for analysis.

It came as Beijing expanded on its earlier claim that the US has been flying its own spy balloons over Chinese airspace, accusing Washington on Tuesday of letting the devices drift over other countries.

China's foreign ministry said the United States had released more than ten high-altitude balloons since May 2022, which then illegally flew into its airspace and that of other countries.

“The US needs to make a thorough investigation and give China an explanation on this,” said Wang Wenbin, a spokesperson for China’s foreign ministry, adding that US balloons had been floating over China since last May.

Washington on Monday said there were no US surveillance aircraft of any kind in Chinese air space.

China’s claims are sowing confusion in the bizarre balloon saga that has further deflated bilateral relations with the US and sparked worries about growing military tensions.

Earlier this month, the US shot down a Chinese balloon that it believed served surveillance and espionage functions. Since then, the US has downed three other airborne objects.

China has continually denied the balloons were linked to the military, saying instead that the one the US downed over the Atlantic Ocean was a weather research “airship” that had merely blown off course.

Other countries, including neighbouring Taiwan, have said they’ve spotted similar balloons in recent years.

The Financial Times this week reported that Taipei had observed dozens of Chinese military balloons in flight in recent years, on average of about once a month, far more than previously known.

Taiwan’s defence ministry has not commented on this report.

But a general denied that they were a security threat on Tuesday.

“The majority of the balloons near our waters were used for meteorological purposes,” said Taiwan Major General Huang Wen-chi on Tuesday.

Beijing claims Taiwan – an island nation with its own democratically-elected government, military, foreign affairs and currency – as its territory. Increased military activities have raised concerns that leader Xi Jinping might try to annex the island by force.

Taiwan has rejected Beijing’s sovereignty claims, as the People’s Republic of China has never governed the island.