The U.S. military said on Wednesday that it had intercepted two Russian and two Chinese military aircraft operating in the Alaska Air Defense Identification Zone, although they stayed in international airspace.

"The Russian and PRC (People's Republic of China) aircraft remained in international airspace and did not enter American or Canadian sovereign airspace," the North American Aerospace Defense Command said in a statement.

It said the aircraft were not seen as a threat and that it would continue to monitor "competitor activity" near North America.