With the world focused on the coronavirus pandemic and North Korea insisting it has not had a single COVID-19 case, the isolated state has carried out four such firings this month.

Unusually, the official Korean Central News Agency (KCNA) did not say in its report that Kim had directed Sunday's test.

The leader is almost always shown overseeing the North's launches but on this occasion KCNA said it was led by ruling party vice chairman Ri Pyong Chol and conducted by the Academy of National Defence Science.

South Korea had said two projectiles -- presumed to be ballistic missiles -- were fired on Sunday from the North Korean port city of Wonsan into the Sea of Japan, also known as the East Sea.

Images carried by the North's official Rodong Sinmun newspaper showed rockets blasting out of a launcher with six firing tubes, striking what appeared to be an island target. Kim was not seen in the photos.

"By Kim's absence, North Korea is trying to reduce the significance of the launch and stressing that the missile test is just a part of normal drills," said Go Myong-hyun, an analyst at the Asan Institute for Policy Studies.

The last time Kim was not seen at such an event was when the North test-fired a new submarine-launched ballistic missile in October, just days before officials from Pyongyang and Washington were due to meet in Stockholm to rekindle stalled diplomacy.

However some analysts believe he was actually present, as some items he habitually uses were visible.

- Virus warnings -

The string of weapons drills come during a prolonged hiatus in disarmament talks with the United States and despite recent overtures from Washington offering help to contain the pandemic.

North Korea has closed its borders to try to protect itself from the novel coronavirus and is one of the few remaining countries yet to report a case of the disease that has killed almost 34,000 people worldwide.

But the virus is likely to have reached the secretive nation, it is widely believed, with health experts warning it could devastate the country given its weak medical infrastructure and widespread malnutrition.

The day after another firing earlier this month, North Korean state media said Kim had received a letter from US President Donald Trump detailing a plan to develop ties -- a move later confirmed by a White House official.

The report cited Kim's powerful sister Kim Yo Jong, who warned that the apparently good personal relationship between the two leaders would not be enough to foster broader relations.

Trump also "expressed his intent to render cooperation in the anti-epidemic work", she said in a statement published by KCNA.

Analysts say the North has been continuing to refine its weapons capabilities more than a year after a summit between Kim and Trump broke down in Hanoi.

Negotiations have since been deadlocked over sanctions relief and what the North would be willing to give up in return.

North Korea is under multiple sets of sanctions from the United Nations, United States and others over its banned weapons programmes.