The South Korean army said that there was no sign of any unusual military response by the North.
An unnamed South Korean army official said the number of artillery mobilized in Thursday’s drills was the biggest ever, adding that the simultaneous shooting in all major frontline areas was a departure from previous exercises.
The border between the two Koreas is the most heavily fortified in the world.
The two countries occasionally exchange gunfire along the frontier and near a disputed maritime border.
In recent years, South Korea has held several joint military drills with the United States.
Pyongyang is irked by joint Seoul-Washington military maneuvers, viewing them as direct threats to its security.
Tensions have been flaring in the region since January when North Korea said it had successfully detonated a hydrogen bomb, its fourth nuclear test, and vowed to build up its nuclear program as deterrence against potential aggression from the US and its regional allies.