Highly appreciating that demonstration fire was carried out satisfactorily as intended: Kim Jong Un

North Korea's leader Kim Jong Un says the country's latest missile launches were a warning to Washington and Seoul over their joint war games, state news agency KCNA reported on Wednesday, as tensions rise on the Korean peninsula.

The latest launch by the nuclear-armed North came after the South Korean and US militaries began mainly computer-simulated joint exercises on Monday to test Seoul's ability to take operational control in wartime.

Those drills are taking place despite Pyongyang's warnings that the exercises would jeopardise nuclear negotiations between the United States and North Korea.

KCNA said Kim had watched the launches early Tuesday, which verified the "war capacity" of the "new-type tactical guided missiles".

With the launches carried out satisfactorily, "Kim Jong Un noted that the said military action would be an occasion to send an adequate warning to the joint military drill now underway by the US and South Korean authorities," KCNA said.

Pyongyang on Tuesday fired two projectiles that "are assumed to be short-range ballistic missiles" into the sea, the South's Joint Chiefs of Staff said earlier.

The latest weapons tests were the fourth pair of projectiles fired in less than two weeks, and the North has threatened more.

US President Donald Trump last week downplayed the North's launches, saying Kim would not want to "disappoint" him.

Trump and Kim held a historic summit in Singapore last year, where the North made a vague pledge on denuclearisation.

A second summit in Hanoi this February broke up amid disagreements over sanctions relief and what Pyongyang might be willing to give up in return.

The two agreed to resume nuclear talks during their impromptu June meeting in the Demilitarized Zone that divides the peninsula, but working-level dialogue has yet to begin.

Analysts say the military manoeuvres on both sides could see discussions pushed back until the autumn, and Pyongyang signalled Tuesday that it was in no mood to talk.

It called the drills a "flagrant violation" of the diplomatic process between Pyongyang, Washington and Seoul.

Pyongyang has always been infuriated by military exercises between the South and US, seeing them as rehearsals for invasion, but in the past it has tended to avoid carrying out missile tests while the war games were taking place.

After the Singapore summit, Trump made a shock announcement halting joint drills, adopting Pyongyang's own description of them as "provocative".

War games known as Ulchi Freedom Guardian (UFG) scheduled for August last year were subsequently suspended and the allies' biggest annual drills, Foal Eagle and Key Resolve, were replaced with a shorter "Dong Maeng" or "Alliance" exercise in March.

US National Security Advisor John Bolton on Tuesday said the latest drills are "consistent with the partnership we have with South Korea.

"North Korea has continued its exercises unabated. So they don't really have a lot to complain about," he told the "Fox and Friends" television show.