North Korea says it will punish the US, after claiming it is conducting spying flights over its territorial waters.
North Korea accused the US of planning a pre-emptive strike
The country's Air Force Command accused the US of carrying out three aerial espionage missions in the last week.
The command said it believed the US was preparing to attack and suggested it would resort to shooting down US spy planes if they continued their flights.
Correspondents say Pyongyang often alleges that spying flights are taking place - the US does not comment.
The Korean People's Army (KPA) Air Force Command said an RC-135 plane had flown over territorial waters on 6, 8 and 10 June .
In a statement it said the US flights were "openly crying out for a pre-emptive attack" on the country.
The command said the espionage missions were a "violent infringement of [North Korea's] sovereignty and a grave violation of international law".
It continued: "The KPA Air Force seriously warns the US imperialists that it will sternly punish the aggressors if their planes continue illegally intruding into the sky ... on espionage missions.
"They had better not forget the wretched fate of the EC-121 large spy plane in the 1960s," it added.
In 1969 North Korean fighters shot a US plane down off the country's east coast, killing all of the 31 crew on board.