Pyongyang: North Korea on Monday accused the United States of flying spy aircrafts into its airspace.
Alleging repeated provocation by the US, North Korea warned that, although exercising restraint, it will shoot down such surveillance flights.
Pyongyang also slammed what it said was a US move to deploy a nuclear missile submarine close to the Korean peninsula.
What North Korea said about its airspace
In a statement, a spokesperson for the North's Ministry of National Defense said "provocative" military actions conducted by the US "several times" were bringing the Korean peninsula closer to a nuclear conflict.
"There is no guarantee that such a shocking accident as the downing of the US Air Force strategic reconnaissance planes will not happen in the East Sea of Korea," the spokesperson added in the statement cited by official news agency KCNA.
There was no immediate response from the US military, while South Korea dismissed North's claim of airspace violation as false. It said the US conducts routine reconnaissance flights around the peninsula.
Escalation through 'nuclear blackmail'
Condemning US plans to deploy strategic nuclear assets around the Korean peninsula, Pyongyang said it is "the most undisguised nuclear blackmail" against North Korea that poses serious threat to peace and security in the region.
In April, the US announced its plan to send a US Navy nuclear-armed ballistic missile submarine to a South Korean port for the first time since the 1980s. It, however, did not share the timeline for the visit.
"Whether the extreme situation, desired by nobody, is created or not on the Korean peninsula depends on the future action of the US, and if any sudden situation happens ... the US will be held totally accountable for it," KCNA said.
Pyongyang cited past incidents when it shot down US planes and warned the US will pay for its "frantically staged" air espionage.