North Korea on Sunday accused the United States and South Korea of conducting more aerial espionage around the peninsula, warning it would take "immediate action" if its sovereignty was breached.

America has deployed dozens of military planes "in air espionage against the DPRK from May 13 to 24," the North's vice defense minister, Kim Kang Il, said in a statement, referring to his country by its official name.

The espionage activities observed over the 12-day time frame were "at a level beyond the wartime situation," he said in the statement, which was carried by the official Korean Central News Agency.