US President Joe Biden ordered a fighter jet to shoot down an unidentified “high-altitude object” off Alaska on Friday, the White House says.

Spokesman John Kirby said the unmanned object was “the size of a small car” and posed a “reasonable threat” to civilian aviation.

The object’s purpose and origin was unclear, Mr Kirby said.

It comes a week after the American military destroyed a Chinese balloon over US territorial waters.

Speaking at the White House on Friday, Mr Kirby said the debris field of the object shot down on Friday was “much, much smaller” than the balloon shot down last Saturday off the coast of South Carolina.

He said that the object was flying at 40,000ft (12,000m) over the northern coast of Alaska.

It had already flown across Alaska at a speed of 20 to 40mph (64km/h) and was out over the sea travelling towards the North Pole, when it was shot down.

Commercial airlines can fly as high as 45,000ft.

Helicopters and transport aircraft have been deployed to collect debris from the frozen waters of the Beaufort Sea.

“We do not know who owns it, whether it’s state-owned or corporate owned or privately owned,” Mr Kirby said.

The object was first spotted on Thursday night, though officials did not specify a time.

He said two fighter jets had approached the object and assessed there was nobody on board, and this information was available to Mr Biden when he made his decision.

“We’re going to remain vigilant about our airspace,” Mr Kirby asserted. “The president takes his obligations to protect our national security interests as paramount.”

According to ABC News, the object seemed to have no propulsion.

It seemed to be floating, “cylindrical and silver-ish grey”, reports the network’s chief global affairs correspondent Martha Raddatz, citing an unnamed US official.

Pentagon press secretary Brigadier General Pat Ryder said the object was “not similar in size or shape” to last week’s Chinese balloon.

He confirmed that an F-22 jet had shot down the object with a sidewinder missile at 13:45 EST (18:45 GMT) on Friday.

The warplane was scrambled from Joint Base Elmendorf-Richardson in Anchorage.

Gen Ryder said a significant amount of debris had been recovered so far. It was being loaded on to vessels and taken to “labs for subsequent analysis”, he added.

Officials said they had not yet determined whether the object was involved in surveillance, and Mr Kirby corrected a reporter who referred to it as a balloon.

He did not specify where exactly the object was shot down, but the Federal Aviation Administration said it had closed about 10 sq miles of US airspace airspace above Deadhorse, northern Alaska, before the F-22 fired.

The site is about 130 miles from the border of Canada, whose Prime Minister Justin Trudeau said on Twitter he had been briefed on the “object that violated American airspace” and “supported the decision to take action”.

No other objects of a threatening nature have been identified above the US at this time, according to the White House.

Mr Kirby said the object did not appear to have the manoeuvrable capability of the Chinese balloon and seemed to be “virtually at the whim of the wind”.

Hours after the US shot down the balloon last Saturday, Defence Secretary Lloyd Austin called his Chinese counterpart via their special crisis line.

But Chinese Defence Minister Wei Fenghe declined to pick up, according to the Pentagon.

Chinese officials on Friday accused the US of “political manipulation and hype”.

In an interview on Thursday, President Biden defended his handling of the Chinese balloon, maintaining that it was not “a major breach”.

Late on Friday, five Chinese companies and one research institute were added to the US government’s trade blacklist. Organisations were placed on the list for their alleged support of Chinese military aerospace programmes – including airships and balloons – the US Commerce Department announced.