The United States and South Korea wrapped up one of their major annual joint military exercises last week, prompting angry retorts and live-fire drills from nuclear-armed Pyongyang, which condemns all such exercises as rehearsals for invasion.

Seoul's military said Monday it had detected the launch of "multiple short-range ballistic missiles" by the North, as US Secretary of State Antony Blinken visited the South Korean capital for talks.

The super-large multiple rocket launcher, referred to as KN-25 by the Seoul-Washington military, is a short-range ballistic missile, according to South Korea's Yonhap news agency.

The North has claimed the weapon has the capability to be equipped with a tactical nuclear warhead.

Pyongyang's official Korean Central News Agency (KCNA) said Kim guided the drills on Monday that tested the "real war capabilities" of 600 millimetre multiple rocket launchers as he stressed the importance of "war preparations".

The drills also involved simulating an aerial explosion of a shell from the super-large multiple rocket launcher at a predetermined altitude above the target, KNCA said.

Kim said the multiple rocket launcher would help the North "block and suppress the possiblity of war with the constant perfect preparedness to collapse the capital of the enemy", according to the report.

During the drills, North Korean artillerymen "demonstrated their excellent crack-shot artillery marksmanship and prompt and thorough combat readiness," it added.

"Massive shells of super-large multiple rocket launchers, which were fired from the sharp gun barrels like lava, flew to the target with the flame of annihilating the enemy," it said.

- More drills -

State media images showed Kim, wearing his customary black leather jacket, watching the drills with his generals and celebrating their apparent success with a raised fist.

Pyongyang this month warned that Seoul and Washington would pay a "dear price" over their military exercises, and later announced that Kim had guided an artillery unit it says was capable of striking the South Korean capital.

Kim last week also oversaw paratroop drills aimed at showing his soldiers' ability to occupy an "enemy region at a stroke", according to state media.

Monday's ballistic missile test was the North's second this year, after Pyongyang launched one tipped with a manoeuvrable hypersonic warhead on January 14.

So far this year, the nuclear-armed North has declared South Korea its "principal enemy", jettisoned agencies dedicated to reunification and outreach, and threatened war over "even 0.001 mm" of territorial infringement.

Seoul is one of Washington's key regional allies, and the United States has stationed about 27,000 American soldiers in the South to help protect it against Pyongyang.

Last week's Washington-Seoul drills included "clearing operations" inside North Korea's "key facilities" in case of an attack by Pyongyang, according to Seoul's military.