The North Korean foreign ministry said U.S. officials seized a diplomatic package from its delegation at John F. Kennedy International Airport on Friday as the diplomats were about to fly home, according to the state news agency.
The North's Foreign Ministry spokesman said a delegation of the North returning from a United Nations conference on the rights of persons with disabilities "was literally mugged" at the John F. Kennedy airport in "an illegal and heinous act of provocation".
The rogue nation threatened unspecified "grave consequences" if the USA failed to provide "a good explanation of its act of infringement upon the sovereignty of the DPRK and an official apology on behalf of the United States government".
"This clearly shows that the U.S. is a felonious and lawless gangster state", the spokesman said in comments carried by the North's official KCNA news agency. While U.S. officials have not revealed what the package contained, the North Koreans claim that they had a valid diplomatic courier certificate for carrying the package.
The ministry also asked the world to "seriously reconsider" NY as a venue for major worldwide events and demanded Washington provide an explanation for infringing upon its sovereignty.
There was no official USA comment on the claims, the News reported.
The State Department and White House had no immediate comment on the North Korean statement.
The accusations came amid mounting tensions over North Korea's repeated testing of ballistic missiles, and controversy over last week's release of ailing former University of Virginia student student Otto Warmbier after 17 months in captivity.
North Korea claimed Mr Warmbier's coma was caused by botulism contracted after his trial previous year and a sleeping pill given to him as treatment.
Continuing military cooperation with South Korea has angered the North, leading to warnings of nuclear war.
The North Korean delegation was returning after the conclusion of a United Nations conference when they were stopped and searched by officials from the Department of Homeland Security.