A smiling Kim Jong-un watched as a major artillery drill was conducted within striking distance of the South Korean capital.

This year Pyongyang has declared Seoul its “principal enemy”, jettisoned agencies dedicated to reunification and outreach, and threatened war over “even 0.001 mm” of territorial infringement.

Wearing a leather jacket and appearing jubilant alongside his generals, the North Korean leader urged his soldiers to “vigorously push forward the work for making preparations for regular combat mobilisation” to “take the initiative with merciless and rapid strikes” in the event of an “actual war”

The remarks came after the United States and South Korea started their annual spring military exercises on Monday with double the number of troops participating compared to 2023.

The North’s live-fire drills on Thursday involved border units “that put the enemy’s capital in their striking range”, Pyongyang’s official Korean Central News Agency (KCNA) said, referring to Seoul.

Seoul’s military also confirmed the North had carried out live-fire artillery drills involving rocket launchers and self-propelled howitzers in the western port city of Nampho.

“Our military is closely monitoring North Korea’s signs of provocation ... while maintaining a firm joint defence posture and conducting the ongoing Freedom Shield exercises and joint drills,” Seoul’s joint chiefs of staff said.

“If North Korea commits a provocation, we will punish overwhelmingly and firmly in accordance with the principle of ‘immediately, strongly, and until the end’.”

On Tuesday North Korea warned that Seoul and Washington would pay a “dear price” over the large-scale military exercises, urging the allies to cease “frantic war drills”.

North Korea has long condemned the joint military exercises, describing them as rehearsals for an invasion.

The nuclear-armed North has in the past carried out weapons tests as a response to such joint exercises.

As he watched the drills on Thursday, Mr Kim “expressed his great satisfaction” that the units are “fully ready for constant mobilisation for battles”, according to KCNA.

On Wednesday, he visited a major operational training base in the country’s western region, with photos released afterwards showing him talking to troops and overseeing firing drills.

Last week, Yoon Suk Yeol, South Korea’s president, called for the international community to back unification efforts to “free everyone on the peninsula”.