SEOUL (Reuters) - North Korea warned of military action should South Korea continue anti-Pyongyang propaganda broadcasts along their shared border, the South’s defense ministry said on Thursday, telling Seoul to halt the loudspeaker broadcasts within 48 hours.

In a statement, the South’s defense ministry said North Korea’s armed forces sent a letter around 5 p.m., calling the South’s propaganda broadcasts a “major challenge” to the North.

South Korea said it fired tens of artillery rounds toward North Korea on Thursday after the North fired a projectile toward a South Korean loudspeaker that had been blaring the propaganda.