"Obviously there is some sort of pattern in there - the fact we are seeing this in a significant degree over the past week is a cause for interest and close attention," Trudeau told reporters in a news conference in Whitehorse, Yukon's capital.

American and Canadian officials have struggled to explain the origin of three objects that U.S. fighter jets have brought down over North American airspace since a suspected Chinese spy balloon was downed on Feb. 4 off South Carolina's coast after flying across the United States.

U.S. military fighter jets on Sunday downed an octagonal object over Lake Huron, the Pentagon said. On Friday, an object was shot down over sea ice near Deadhorse, Alaska, and a third object, cylindrical in shape, was destroyed over Canada's Yukon on Saturday, with investigators still hunting for the wreckage, officials said.

Trudeau said search and recovery efforts were underway for the aerial object shot down over Yukon, adding that winter weather was posing challenges. Trudeau also said he would discuss the issue of aerial objects with U.S. President Joe Biden when they meet in March.

The presence of those aerial objects in North American airspace was a "very serious situation," Trudeau said.

Asked why Canada itself did not shoot down the object over Yukon, Trudeau said: "NORAD (North American Aerospace Defense Command) is a joint command, which means we do things together over North America, and there were Canadian and American fighter jets scrambled to intercept the object and to take it down."

Trudeau added, "Our focus was not on which side gets credit for what."

The United States and China traded claims about alleged spy balloons on Monday. China said that U.S. high-altitude balloons had flown over its airspace without permission more than 10 times since the beginning of 2022. The White House promptly denied it.