The move comes as nuclear negotiations with the United States are at a standstill and as a unilateral deadline Pyongyang set Washington to offer it fresh concessions on sanctions relief expired.

The two devices were fired eastwards over the sea from the Wonsan area on the east coast, the South's Joint Chiefs of Staff said.

"The military is monitoring for additional launches and maintaining readiness," the statement added.

Pyongyang carried out a series of weapons tests late last year, the last of them in November, often describing them as multiple launch rocket systems, although others called them ballistic missiles.

It also carried out static engine tests, most recently in December.

At a party meeting at the end of that month, leader Kim Jong Un declared that Pyongyang no longer considered itself bound by its moratoriums on nuclear and intercontinental ballistic missile tests, and threatened a demonstration of a "new strategic weapon" soon.

North Korea has a long history of seeking to demonstrate its military capability to try to obtain concessions.

The latest launches come as Pyongyang tries to prevent a nationwide coronavirus outbreak, which analysts say would wreak havoc in the ill-equipped country.

"March is pretty reliably missile-testing season for North Korea," tweeted Ankit Panda, senior fellow at the Federation of American Scientists.

"Looks like COVID-19 hasn't changed that (or Pyongyang is determined to make it appear as if it hasn't)," he added.

North Korea has not reported a single case of the coronavirus, which has killed more than 3,000 people and infected over 88,000 in dozens of countries since it emerged in neighbouring China.

- Joint exercises -

Seoul and Washington last week said they will postpone forthcoming joint military exercises after South Korea -- which has more than 4,000 new cases -- declared its highest "severe" alert level over the coronavirus.

The United States has 28,500 troops in South Korea to protect it against the nuclear-armed North, many of them based south of Seoul at Camp Humphreys in Pyeongtaek -- Washington's biggest overseas military facility.

The security allies have previously scaled back annual joint military exercises significantly to facilitate nuclear talks with Pyongyang -- which condemns such drills as preparations for an invasion -- but a command coordination exercise had been planned for this spring.

In the past Pyongyang has fired missiles capable of reaching the entire US mainland and has carried out six nuclear tests, the last of them 16 times more powerful than the Hiroshima blast, according to the highest estimates.

It is under multiple sets of sanctions over its weapons programmes from the United Nations Security Council, US, South and other bodies.

Heightened tensions in 2017 were followed by two years of nuclear diplomacy between Pyongyang and Washington, including three meetings between Kim and US President Donald Trump, but little tangible progress was made.