Utah - A small balloon floating at a high altitude over Utah was intercepted by fighter aircraft on Friday but deemed to pose no national security or flight risk, a US-Canada military agency said.

The North American Aerospace Defense Command (NORAD) said in a statement it had detected the balloon traveling at an altitude between 43,000-45,000 feet, CBS News reported.

"The balloon was intercepted by NORAD fighters over Utah, who determined it was not maneuverable and did not present a threat to national security," the joint agency said.

The US Federal Aviation Administration (FAA) "also determined the balloon posed no hazard to flight safety," according to NORAD.

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"NORAD will continue to track and monitor the balloon," it added.

An unnamed US official told CBS News the balloon had a cube-shaped box about two feet long on each side hanging below it.

In February last year, the United States shot down a huge white balloon from China after it was spotted over a series of nuclear weapons sites.

Beijing denied it was a spy balloon, saying the craft was used for weather research and had blown off-course.