The ministry in charge of inter-Korean affairs issued a "stern warning" to North Korea over its threats after the South Korean Constitutional Court struck down a law banning anti-Pyongyang leaflet activity.

Seoul's unification ministry issued a statement on Thursday, saying leaflet campaigns are voluntary acts conducted by civic groups in line with the constitutionally guaranteed freedom of expression, which the court cited in its ruling.

The ministry then strongly warned the North to refrain from rash acts under the pretext of a response to the Constitutional Court's decision.

On Wednesday, the North issued a threat through the state-run Korean Central News Agency to "pour a shower of shells" into South Korea as punishment over the anti-Pyongyang propaganda leaflets.