North Korean leader Kim Jong Un supervised his second live-fire artillery exercise in a week, state media said on Tuesday, as the country continues to expand its military capabilities.

The report by Pyongyang's Korean Central News Agency (KCNA) came a day after South Korea's military detected the launch of three short-range projectiles from North Korea's eastern coast.

KCNA said Kim showed great satisfaction as his front-line artillery units demonstrated "excellent marksmanship" during the exercise that tested their abilities to execute quick counterattacks.

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Pyongyang's official Rodong Sinmun newspaper published photos of rockets blasting out of multiple-rocket launchers and striking what appeared to be an island target.

Kim, wearing a black fur hat and carrying binoculars, was shown watching from a trench, alongside a military officer who, unlike Kim, was wearing a black facemask in an apparent reflection of the country's campaign against the new coronavirus.

The KCNA said Kim promised to build his artillery force into the "world's strongest arms of service everyone is afraid of" but did not mention any comments directed at the United States or South Korea.

Seoul's Joint Chiefs of Staff said the projectiles fired from the eastern coastal town of Sondok flew as far as 200 kilometres (125 miles) at a maximum altitude of 50km (30 miles) before landing in the waters between the Korean Peninsula and Japan.

Kim also oversaw artillery exercises on February 28 and March 2, as the country resumed weapons tests for the first time since November, a lull that some experts said could have been caused by the country's toughened preventive measures to fend off COVID-19.

North Korea has not publicly confirmed a single case of the illness, but its state media have reported that thousands of people have been quarantined as part of strict prevention measures.

Kim had entered the new year promising to bolster his nuclear deterrent in face of "gangster-like" US sanctions and pressure.

Nuclear talks have stalled since the collapse of the second summit between Kim and US President Donald Trump in early 2019 when the Americans rejected North Korean demands for significant sanctions relief in exchange for a partial surrender of its nuclear capabilities.