North Korea is warning Monday that it may start shooting down U.S. Air Force spy planes after accusing an American military aircraft of "illegally" intruding into its airspace "several times." 

The threat published in North Korean state media was attributed to a spokesman for the country’s Ministry of National Defense and comes after U.S. Forces Korea said it conducted joint aerial drills with South Korea in late June. 

"This month alone, RC-135, U-2S and RQ-4B, strategic reconnaissance planes and reconnaissance drone belonging to the U.S. Air Force, flew over the East and West seas of Korea in turn for eight straight days from July 2 to 9 to conduct provocative aerial espionage on the DPRK's strategic interior," read the statement posted by the Korean Central News Agency. 

"In particular, a strategic reconnaissance plane of the U.S. Air Force illegally intruded into the inviolable airspace of the DPRK over its East Sea tens of kilometers several times," it added, without elaborating. 

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US South Korea joint air drill

U.S. B-52H bombers, center, F-16 fighter jets, top, and South Korean F-35A fighter jets, bottom right, fly over the Korean Peninsula during a joint air drill in South Korea on April 14, 2023. (South Korea Defense Ministry via AP)

The spokesman said North Korea is "now maintaining our utmost patience and self-control, but everything has its limit." 

"There is no guarantee that such [a] shocking accident as [a] downing of the U.S. Air Force strategic reconnaissance plane will not happen in the East Sea of Korea," he reportedly added. 

Kim Yo Jong, who is Kim Jong Un's sister, later accused the U.S. of sending spy planes over the North’s exclusive economic zone, the area within 200 nautical miles of its territory where it controls rights to natural resources.

Kim said a U.S. spy plane crossed the eastern sea boundary between the Koreas at around 5 a.m. Monday and conducted reconnaissance activities over the North’s exclusive economic zone before being chased away by North Korean warplanes. She said the U.S. aircraft crossed the eastern sea boundary again at around 8:50 a.m., prompting North Korea’s military to issue an unspecified "strong warning" toward the United States.

"A shocking incident would occur in the long run in the 20-40 kilometer section in which the U.S. spy planes habitually intrude into the sky above the economic water zone," she said, according to The Associated Press.

Kim Yo Jong North Korea

Kim Yo Jong, sister of North Korea's leader Kim Jong Un, attends a wreath-laying ceremony at Ho Chi Minh Mausoleum in Hanoi, Vietnam, March 2, 2019. Kim Yo Jong alleged on Monday, July 10, 2023, that the North's warplanes repelled a U.S. spy plane that flew above the country's exclusive economic zone. (Jorge Silva/Pool Photo via AP)

U.S. Forces Korea did not immediately respond Monday to a request by Fox News Digital for its reaction. South Korea’s military did tell Reuters that the North’s claims of airspace violations are not true, and that the U.S., a key ally, often conducts reconnaissance flights in the region. 

Apparently in response to that comment, Kim accused South Korea's Joint Chiefs of Staff of acting like a "spokesperson" for the U.S. military and said the U.S. has been intensifying its reconnaissance activities in a serious infringement of North Korea's sovereignty and safety.

North Korea military parade in Pyongyang

Troops fire a gun salute during a military parade to mark the 75th founding anniversary of North Korea's army, in Pyongyang, on Feb. 8, 2023. (KCNA/Reuters)

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On June 30, U.S. Forces Korea said the "Republic of Korea Air Force and the United States Air Force conducted a combined aerial training event with U.S. Air Force B-52H Stratofortresses over the Korean Peninsula." 

"The ROK-U.S. combined aerial training event consisted of ROK Air Force F-35’s, KF-16's and U.S. Air Force F-16’s and F-15's escorting the U.S. B-52 strategic bombers as they entered the Korean Air Defense Identification Zone to conduct a combined flight training," they said. 

U.S. Forces Korea added that the training "offered the alliance an opportunity to further strengthen its interoperability by demonstrating a combined defense capability, rapid deployment, and extended deterrence in the defense of the Korean Peninsula." 

US submarine in South Korea

The U.S. nuclear-powered submarine USS Michigan is anchored at a port in Busan, South Korea, on June 16, 2023. (Reuters/Yonhap)

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In mid-June, the U.S. also deployed a nuclear-powered submarine capable of carrying around 150 Tomahawk missiles to South Korean waters, according to The Associated Press. 

The North Korean defense spokesman on Monday called that deployment "a very dangerous situation." 

The Associated Press contributed to this report.