North Korea has warned that any attempt to shoot down a satellite it says it plans to launch will result in war.
The South and the US believe Pyongyang could be preparing to test-fire a long-range missile under the guise of a satellite launch.
The North also says it has put its military on full combat alert as an annual military exercise by US and South Korean forces begins.
The official news agency called the manoeuvres a dangerous provocation.
On Friday, the North said that the risk of conflict resulting from the drill meant it could no longer guarantee the safety of commercial flights through airspace it controls off the east coast.
A number of airlines have already re-routed their flights as a precaution.
In a statement published by the official Korean Central News Agency on Monday, the Korean People's Army warned that it was ready to use force
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