LONDON -- British Prime Minister Rishi Sunak said Monday that the government would do "whatever it takes" to protect the country, as the U.K. announced a security review after several unidentified objects were shot down in the skies over North America.

Asked about the objects, Sunak said he wouldn't "comment in detail on security matters, but people should be reassured that we have all the capabilities in place to keep the country safe," including a quick-reaction force of Typhoon fighter jets.

Defense Secretary Ben Wallace said "the U.K. and her allies will review what these airspace intrusions mean for our security."

He said "this development is another sign of how the global threat picture is changing for the worse."

U.S. fighter jets shot down an object over Lake Huron on Sunday -- the fourth such downing over the U.S. or Canada this month.

On Feb. 4, the U.S. military downed what officials say was a Chinese spy balloon off the South Carolina coast after tracking it for several days across North America.

On Friday, F-22 jets shot down a "car-sized" object in U.S. airspace off the coast of Alaska, and on Saturday Canadian Prime Minister Justin Trudeau said he had ordered a U.S. warplane to shoot down an unidentified object -- later described as a balloon -- high over the Yukon territory in northwest Canada.

The item downed Sunday was described as octagonal, with strings hanging off, but had no discernable payload.

The three objects were much smaller in size, different in appearance and flew at lower altitudes than the suspected spy balloon -- one of what U.S. officials say is a fleet of Chinese aerial surveillance balloons that have targeted more than 40 countries over several years.

China says the unmanned balloon was a civilian meteorological airship that had blown off course.

British Transport Minister Richard Holden said Monday that it was "possible" China had flown spy balloons over the U.K. He said Britain would deal "robustly" with China, which he called "a hostile state."

A senior U.S. military official said Sunday that part of the reason for the repeated shootdowns is a "heightened alert" and closer scrutiny of the skies following discovery of the spy balloon.

Pentagon officials say the three objects downed since then posed no security threats, but so far little is known about them and officials have ruled nothing out -- not even UFOs.