North Korea condemned the top U.S. diplomat in Seoul for flying over South Korean airspace in a U.S. F-16 fighter jet. File Photo by Matthew Allen Hecht/Flickr

SEOUL, July 19 (UPI) -- North Korea denounced the U.S. ambassador to Seoul for flying over South Korean airspace in an F-16 fighter jet.

Ambassador Mark Lippert had flown on the U.S. aircraft last week and is said to have asked for joint defense readiness, local news network KBS reported.


But on Tuesday a North Korean foreign ministry spokesman condemned the flight as an "evil, vicious" act, according to Yonhap.

"At this point when the heavy black clouds of nuclear war have gathered over the Korean peninsula it is a very significant development in U.S. North Korea policy that the U.S. ambassador in South Korea took a flight on a fighter jet," the spokesman said in an interview with state-controlled KCNA.

"It cannot be anything else but an inconceivably evil, vicious act that could only be the work of an insane madman," the North Korean spokesman said.

Pyongyang said the U.S. diplomat's flight over South Korean airspace was a warning of events to come, that, according to the spokesman, is to include "unprecedented action" on the Korean peninsula that could take place in the near future.

North Korea also called the upcoming joint military exercises, Ulchi Freedom Guardian, a practice drill for an invasion.

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"We are carefully watching such movements from the United States and taking precautions. We will strengthen our nuclear deterrent to protect our nation's sovereignty and people's survival from the U.S. nuclear threat," North Korea said.

Yonhap reported Tuesday North Korea has also resumed the broadcasting of encrypted numbers.

The method has been used in the past to deliver missives to operatives in the South, according to an anonymous South Korean government source.

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The broadcasts began early Friday, the source said.