NORTH Korea has fired what appeared to be two short-range ballistic missiles into the sea, according to South Korea’s military.

The launches are the fifth round in less than three weeks in what is being seen as a protest at the slow pace of nuclear negotiations with the United States and the continuance of US-South Korea joint military exercises.

South Korea’s military alerted reporters to the launches hours after US president Donald Trump said he received a “beautiful” three-page letter from North Korean leader Kim Jong Un and predicted that they will have more talks to try resolving the nuclear stand-off.

Trump reiterated that he was not bothered by the flurry of short-range weapons Kim has launched despite the growing threat they pose to US allies in the region.

In a series of Tweets, Trump said: “In a letter to me sent by Kim Jong Un, he stated, very nicely, that he would like to meet and start negotiations as soon as the joint U.S./South Korea joint exercise are over.

“It was a long letter, much of it complaining about the ridiculous and expensive exercises.

“It was also a small apology for testing the short-range missiles, and that this testing would stop when the exercises end. I look forward to seeing Kim Jong Un in the not too distant future!

“A nuclear free North Korea will lead to one of the most successful countries in the world!”

South Korea’s Joint Chiefs of Staff said the presumed ballistic missiles were fired from the North’s eastern coast and flew about 250 miles on an apogee of 30 miles, before landing in waters between the Korean Peninsula and Japan.

Seoul’s presidential Blue House said the tests were likely aimed at verifying the reliability of the North’s newly developed weapons and also demonstrating displeasure over the allied drills.

The North has unleashed a series of test firings of short-range weapons in recent weeks while saying that the joint military drills between the allies compel it to “develop, test and deploy the powerful physical means essential for national defence”.

Experts say Trump’s downplaying the North’s launches allowed the country more room to intensify its testing activity while it seeks to build leverage ahead of negotiations, which could possibly resume sometime after the end of the allies’ drills later this month.

Leif-Eric Easley, an expert at Seoul’s Ewha Woman’s University, said North Korea is also looking to exploit Trump’s preoccupation with getting South Korea to pay more for US troop deployment in the country as well as Seoul’s worsening relations with Tokyo.

South Korea has threatened to end a military intelligence-sharing agreement with Japan in what is seen as an attempt to pressure the United States into mediating the dispute.

“Kim appeals to Trump directly about the exercises, trying to drive a wedge between Washington and Seoul,” Easley said.

“Meanwhile, North Korean propaganda supports rising anti-Japan sentiment in South Korea, calculating that a diplomatically isolated Seoul will be more subject to Pyongyang’s coercion.”

The North’s recent tests have dampened the optimism that followed the third and latest meeting between the leaders of the United States and North Korea on June 30 at the inter-Korean border.