North Korea raised the stakes Friday by warning of “surprise operations” along its frontline if South Korea does not stop psychological warfare broadcasts by 5 p.m. on Saturday.

The ultimatum, also sent directly to South Korea’s military via a West Sea communications line on Thursday afternoon, also said that “frontline large combined units of the KPA” would be put into a state of “semi-war” as of 5 p.m. on Friday.

“Unless (South Korea) stops psychological broadcasting towards the north and dismantle(s) all means for psychological warfare within 48 hours … the KPA (will) launch a strong military action,” a state media description