Washington DC - There is no indication aliens or extraterrestrial activity are behind a series of unidentified objects shot down over the US, the White House said on Monday.

Four unmanned objects have been shot down, with the latest being downed over Lake Huron on the order of President Joe Biden.

"I don't think the American people need to worry about aliens with respect to these crafts, period," National Security spokesperson John Kirby said at a press conference on Monday.

Press Secretary Karine Jean-Pierre said she was aware questions and concerns had been raised about aliens.

Donald Trump Trump threatens Republican congressman with a primary challenge for refusing to raise debt ceiling

"There is no, again, no indication of aliens or extraterrestrial activity with these recent takedowns," she said.

"It was important for us to say that from here because we've been hearing a lot about it."

Jean-Pierre said the US was still trying to assess what the latest object was.

"I think we all need to be humble here in terms of what our ability is to positively identify stuff from fighter aircrafts that are going several hundred miles an hour past, essentially, in terms of relative motion, a stationary object that was not very big," she said.

Officials still did not know exactly what the object looked like, its purpose, or who owned it.

Joe Biden Fade out: Biden disappears into background ahead of Trump inauguration

"We hope to be able to find out more once we can recover the debris from that one and from the other two as well."

The US shot down an object flying over Alaska on Friday and another over Canada on Saturday.

The events come a week after the Pentagon shot down a suspected Chinese surveillance balloon off the Atlantic coast of South Carolina.