The US has shot down an unknown object flying in its airspace, off the coastline of Alaska – just days after it downed a Chinese “spy” balloon.

The object, shot down on the order of President Joe Biden, was flying at a high altitude of about 40,000ft and was the size of a small car, the White House said.

It posed a “reasonable threat” to the safety of civilian flights, said John Kirby, the White House National Security Council spokesman.

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It was unclear where the object came from.

“We don’t know who owns this object,” said Mr Kirby.

US officials said: “Out of an abundance of caution and at the recommendation of the Pentagon, President Biden ordered the military to down the object over water.”

An F-22 aircraft took down the object using a Sidewinder missile over territorial waters – now frozen.

There was no indication the object was manned, nor did the Pentagon know what speed it was travelling at.

The incident happened just days after the US downed a Chinese balloon believed to be a spy aircraft.

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How US shot down China’s ‘spy balloon’

China maintained the balloon was an airship for scientific research that had accidentally flown over the US.

That balloon was shot down by fighter jets off the coast of South Carolina – with the US military starting to collect the debris shortly thereafter.

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Moment ‘spy balloon’ is shot down

The incident sparked a diplomatic row between China and the US, with secretary of state Antony Blinken postponing a visit to China that had been due to start just a few days later.

Why are US officials unable or unwilling to tell us more?

There were two news conferences today – from the White House and from the Pentagon. Yet officials were unable to give many details or answer the central question: what was it?

“We’re calling this an object, because that’s the best description we have right now,” an official from the National Security Council said from the White House podium. Over at the Pentagon they could offer little more.

They think it was unmanned – that was the assessment of the two fighter jet pilots. It was at 40,000 feet – so at least 20,000 feet lower than the Chinese balloon shot down six days ago. But what was it?

Was it another balloon carrying a payload? Was it some other type of flying object? A drone?

They had good enough sight of it, overnight and again today, to determine its approximate size (they likened it to a small car) and to determine that it was “likely not manned”. So surely they have a good idea of what type of flying object it was? Why are they unable or unwilling to tell us more?

Are they drawing any links with China? Again, they wouldn’t say, but did confirm that there had been no attempt to contact the Chinese either before or after this shootdown.

When the balloon was shot down on Saturday, US Defence Secretary Lloyd Austin attempted to call his Chinese counterpart.

The “spy” balloon was believed to have flown over the Aleutian Islands, off the coast of Alaska, and through Canada before entering the US.

Officials said they were “confident” the balloon was “seeking to monitor sensitive sites” and they sought “to recover it”.

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Military and defence leaders had considered shooting the balloon out of the sky but decided against it due to the safety risk from falling debris.

The balloon was flying between 60,000ft and 65,000ft before it was shot down, spreading debris across seven miles, according to US officials.