A US fighter jet shot down an unidentified object over Canada on Saturday, the second such incident in North American skies since the dramatic downing of a suspected Chinese spy balloon a week ago.

Prime Minister Justin Trudeau said a joint US-Canadian military operation led to the takedown of the object, the latest in a series of mysterious air intrusions.

"Canadian and US aircraft were scrambled, and a US F-22 successfully fired at the object," Trudeau tweeted Saturday.

Shortly after the 3:41 pm (2041 GMT) downing of the object, aviation authorities shut down part of the airspace over the northwest US state of Montana after detecting what they called a "radar anomaly," the US Northern Command said.

In a sign of jitters over possible intrusions, Northern Command said US fighter jets took to the skies but "did not identify any object to correlate to the radar hits." Skies were then reopened to commercial air traffic.

The object shot down in the Yukon was "small, cylindrical" in shape, said Canada's defense minister, Anita Anand.

"The object was flying at an altitude of approximately 40,000 feet, had unlawfully entered Canadian airspace, and posed a reasonable threat to the safety of civilian flight," Anand told reporters.

Trudeau said Canadian forces in the Yukon "will now recover and analyze the wreckage of the object."

He said he spoke with US President Joe Biden over the latest incursion, while Anand also said she spoke with US Defense Secretary Lloyd Austin.

The new incursions into Alaska and the Yukon came after the United States said Wednesday that suspected Chinese spy balloons like the one it shot down February 4 were part of a "fleet" that has spanned five continents. NATO also voiced concern.

Anand, however, said "it would not be prudent for me to speculate on the origins of the object at this time."

US and Canadian planes flew together to take on the object Saturday, the US Department of Defense and Anand said.

"President Biden authorized US fighter aircraft assigned to NORAD to work with Canada to take down a high-altitude airborne object over northern Canada today," Pentagon Spokesman Pat Ryder said in a statement, referring to the North American Aerospace Defense Command.

An F-22 fighter jet fired an AIM 9X missile that brought it down, he said.

The White House said Biden and Trudeau spoke Saturday, and "commended NORAD's and US Northern Command's strong and effective partnership and agreed to continue their close coordination to detect, track, and defend our airspace."

The object taken out over the Yukon, which borders Alaska, came after fighter jets downed another object Friday off the US state's north coast near the village of Deadhorse.

Search and recovery operations for the remains of that object continued Saturday but were hindered by Arctic "wind chill, snow, and limited daylight," Northern Command said in a statement.

"Recovery activities are occurring on sea ice," it said, adding that the Pentagon could offer "no further details... about the object, including its capabilities, purpose, or origin."

- Diplomatic riff -

A giant balloon carrying electronics -- which the Pentagon described as a spy vessel -- flew over Canada and the United States last month, sparking a diplomatic flare-up with China, which acknowledged ownership of what it said was a harmless weather balloon blown off course.

That balloon crossed into US airspace in Alaska on January 28, traversing Canada and much of the United States -- and prompting the scrapping of a rare trip to Beijing by US Secretary of State Antony Blinken -- before it was shot down over the Atlantic Ocean off South Carolina on February 4.

The balloon's path took it over several US military installations, including ones with silos of nuclear-tipped intercontinental ballistic missiles.

Biden's decision to allow the balloon to cross the mainland unimpeded before shooting it down over water was hammered by Republican lawmakers, some of whom said it should have been shot down upon entering US airspace.

Federal recovery teams, comprising both divers and unmanned remote-control minisubs, continue to survey for debris of the balloon in shallow coastal waters, the Northern Command statement said.

US officials say images of the balloon show it had surveillance equipment that could intercept telecommunications as well as a solar array to power multiple sensors.