WASHINGTON: US Secretary of State Mike Pompeo on Monday called for the immediate release of two Canadians charged by China for alleged espionage, saying the United States was "extremely concerned" and that the two men's detention was unjustified.

"These charges are politically motivated and completely groundless," Pompeo said in a statement. Chinese prosecutors announced the charges on Friday against former diplomat Michael Kovrig and businessman Michael Spavor, who were arrested in late 2018.