A US senator has called for mysterious drones spotted flying at night over sensitive areas in New Jersey and other parts of the Mid-Atlantic region to be "shot down, if necessary", even as it remains unclear who owns the unmanned aircraft.

"We should be doing some very urgent intelligence analysis and take them out of the skies, especially if they're flying over airports or military bases," Senator Richard Blumenthal of Connecticut said today, as concerns about the drones spread across Capitol Hill.

People in the New York region were also concerned that the drones might be sharing airspace with commercial airlines, he said, demanding more transparency from the Biden administration.

The White House said today that a review of the reported sightings showed that many of them were actually manned aircraft being flown lawfully. White House National Security spokesman John Kirby said there were no reported sightings in any restricted airspace. He said the US Coast Guard has not uncovered any foreign involvement from coastal vessels.

"We have no evidence at this time that the reported drone sightings pose a national security or a public safety threat, or have a foreign nexus," Kirby said, echoing statements from the Pentagon and New Jersey Governor Phil Murphy.

Pentagon spokesperson Sabrina Singh has said they were not US military drones.

In a joint statement issued today, the FBI and the Department of Homeland Security said they and their federal partners, in close coordination with the New Jersey State Police, "continue to deploy personnel and technology to investigate this situation and confirm whether the reported drone flights are actually drones or are instead manned aircraft or otherwise inaccurate sightings".

The agencies said they have not corroborated any of the reported sightings with electronic detection, and that reviews of available images appeared to show many of the reported drones were actually manned aircraft.

"There are no reported or confirmed drone sightings in any restricted air space," according to the statement.

The drones appear to avoid detection by traditional methods such as helicopter and radio, according to a state lawmaker briefed Thursday by the Department of Homeland Security.

The number of sightings has increased in recent days, though officials say many of the objects seen may have been planes rather than drones. It's also possible that a single drone has been reported more than once.

The worry stems partly from the flying objects initially being spotted near the Picatinny Arsenal, a US military research and manufacturing facility, and over President-elect Donald Trump's golf course in Bedminster.

In a post on the social media platform X, Assemblywoman Dawn Fantasia described the drones as up to 1.8m in diameter and sometimes travelling with their lights switched off.

Drones were legal in New Jersey for recreational and commercial use but were subject to local and Federal Aviation Administration regulations and flight restrictions. Operators must be FAA certified.

Most, but not all, of the drones spotted in New Jersey appeared to be larger than those typically used by hobbyists.

Senator Cory Booker of New Jersey said he was frustrated by the lack of transparency, saying it could help spread fear and misinformation.

"We should know what's going on over our skies," he said.

John Duesler, president of the Pennsylvania Drone Association, said witnesses might be confused about what they were seeing, especially in the dark, and noted it was hard to know the size of the drones or how close they might be.

"There are certainly big drones, such as agricultural drones, but typically they are not the type you see flying around in urban or suburban spaces," Duesler said.

Duesler said the drones — and those flying them — likely could not evade detection.

"They will leave a radio frequency footprint, they all leave a signature," he said. "We will find out what kind of drones they were, who was flying them and where they were flying them."

Fantasia, a Morris County Republican, was among several lawmakers who met with state police and Homeland Security officials to discuss the sightings from the New York City area across New Jersey and westward into parts of Pennsylvania, including over Philadelphia. It was unknown at this time whether the sightings were related.

Duesler said the public wanted to know what was going on.

"I hope [the government agencies] will come out with more information about this to ease our fears. But this could just be the acts of rogue drone operators, it's not an 'invasion' as some reports have called it," Duesler said. "I am concerned about this it but not alarmed by it."