The North Korean leader’s influential sister threatened “terrible and fatal” retaliation against Seoul on Tuesday, following South Korea and Ukraine’s recent allegations that Pyongyang has dispatched troops to support Russia’s invasion.

In a statement released through the state-owned Korean Central News Agency on Tuesday evening, Kim Yo Jong accused the two countries of provoking “nuclear weapons states,” without specifying what actions have drawn Pyongyang’s ire.

“A military provocation against a nuclear weapons state may lead to a horrible situation, unimaginable for politicians and military experts in any big or small country in the world with their normal thinking to experience,”