North Korea threatened to shoot down U.S. reconnaissance planes flying off its east coast in a statement Monday, accusing Washington of raising tensions with such flights and plans to send a nuclear submarine to South Korea.

These perceived provocations “raise military tensions to another level and force us to accept the fact of the worst state of nuclear crisis,” an unnamed defense ministry spokesperson said, echoing recent warnings of being on the “brink of a nuclear war.”

“There is no guarantee there won’t be a shocking incident where a U.S. military strategic reconnaissance plane is shot down off the [DPRK]