Kim Jong Un observed missile firing drills
North Korean state media has said leader Kim Jong Un observed a live-fire drill of long-range multiple rocket launchers and unspecified tactical guided weapons.
It came a day after South Korea's military detected the North launching several unidentified short-range projectiles into the sea off its eastern coast.
Pyongyang's official Korean Central News Agency (KCNA) said Mr Kim expressed "great satisfaction" over Saturday's drills and stressed that his front-line troops should keep a "high alert posture" and enhance combat ability to "defend the political sovereignty and economic self-sustenance of the country".
The weapons launches were a likely sign of Pyongyang's growing frustration at stalled diplomatic talks with Washington meant to provide coveted sanctions relief in return for nuclear disarmament.
They also highlighted the fragility of the detente between the Koreas, which in a military agreement reached last September vowed to completely cease "all hostile acts" against each other in land, air and sea.
South Korea said it was "very concerned" about North Korea's weapons launches, calling them a violation of the agreements to reduce animosities between the countries.
The statement, issued after an emergency meeting of top officials at the presidential Blue House in Seoul on Saturday, also urged North Korea to stop committing acts that would raise military tensions and join efforts to resume nuclear diplomacy.
KCNA said Mr Kim had praised the People's Army for "its excellent operation of modern large-calibre long-range multiple rocket launchers and tactical guided weapons".
The North's official Rodong Sinmun newspaper published photos that showed Mr Kim, equipped with binoculars, observing tests of different weapons systems, including multiple rocket launchers and what appeared to be a short-range missile fired from a launch vehicle, and also an explosion of what seemed to be a target set on island rocks.
South Korea's Joint Chiefs of Staff said that "several projectiles" had been launched from near the coastal town of Wonsan and that they flew up to 125 miles before splashing into the sea towards the north-east.
That roughly matched the distance between the area and the South Korean capital of Seoul, although in Sunday's report the North did not issue any direct threat or warning towards the South or the United States.
Experts say the North may increase these sorts of low-level provocations to apply pressure on the United States to agree to reduce crushing international sanctions.
The launches comes amid a diplomatic breakdown that has followed the failed summit earlier this year between US president Donald Trump and Mr Kim over the North's pursuit of nuclear bombs that can accurately target the US mainland.
Mr Trump said on Saturday that he still believed a nuclear deal with North Korea would happen. He tweeted that Mr Kim realises "the great economic potential of North Korea, & will do nothing to interfere or end it".
He added: "He also knows that I am with him & does not want to break his promise to me. Deal will happen!"
North Korea last conducted a major missile test in November 2017 when it flight-tested an intercontinental ballistic missile that demonstrated potential capability to reach deep into the US mainland. That year saw a string of increasingly powerful weapons tests from the North and a belligerent response from Mr Trump that had many in the region fearing war.
During the diplomacy that followed those weapons tests, Mr Kim said that the North would not test nuclear devices or ICBMs. The short-range projectiles launched on Saturday do not appear to violate that self-imposed moratorium, and they may instead be a way to register Mr Kim's displeasure with Washington without having the diplomacy collapse.