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Photo for illustrative purposes only Image Credit: Pixels

WASHINGTON: The White House insisted Monday that mystery drones which have caused a public panic in parts of the United States were flying legally, after President-elect Donald Trump suggested there had been a government cover-up.

Trump said the US government "knows what is happening" as he weighed on the flurry of sightings over New Jersey and New York that have sparked something increasingly akin to mass panic.

Outgoing President Joe Biden's administration has faced mounting criticism for not clearly identifying the origins of the objects, but on Monday it rejected any suggestion of a cover-up.

National Security Council spokesman John Kirby insisted the government was being "open and transparent," and said most sightings involved drones operating "legally and lawfully."

"We assess that the sightings to date include a combination of lawful commercial drones, hobbyist drones and law enforcement drones, as well as manned fixed-wing aircraft, helicopters and even stars that were mistakenly reported as drones," Kirby told reporters.

"We have not identified anything anomalous or any national security or public safety risk."

The assessment was made by law enforcement officials "having closely examined the data, having closely looked at the tips and collated them the best we can from concerned citizens," Kirby said.

Top US officials have previously rejected any suggestion of foreign involvement - including far-fetched claims that the drones originated from an Iranian or Chinese "mothership" out at sea - even as public concern has mounted.

Video footage of recent mysterious airborne phenomena has clogged social media, with spottings also reported in Maryland and Virginia.

 'Something strange' 

Trump, whose cabinet contains a number of conspiracy theorists on subjects including vaccines and foreign policy, weighed in on the topic as he gave his first full post-election press conference.

"The government knows what is happening," he said at his Mar-a-Lago resort in Florida, without offering any evidence to back up his claim.

"Our military knows and our president knows. And for some reason they want to keep people in suspense."

Trump, who is due to take office for his second term on January 20, said he didn't think it was "the enemy" behind the drones "because if it was the enemy they'd blast it out."

But he added that "something strange is going on."

The Republican said some of the drones had been seen over his golf course in Bedminster, New Jersey, adding that he had abandoned plans to spend the weekend there as a result.

Trump, who has repeatedly criticized Biden's outgoing administration on a number of fronts, had earlier urged US authorities to identify the drones' origins in a social media post on Friday.

After an initially slow response to the public fears, the White House has moved to get ahead of the news as the story about the drones makes headlines worldwide.

The US Homeland Security chief had insisted on Sunday in a special briefing that there was no security threat.

But some criticism has come even from Biden's own party, with top Democratic Senator Chuck Schumer calling Sunday for action to make it easier for US authorities to "bring down" any drone seen to pose a threat.

Boston police announced Sunday that two Massachusetts men had been arrested the previous night for allegedly conducting a "hazardous drone operation" near the city's Logan International Airport.

AFP