North Korea on Saturday said that it has tested a 'new weapon' under the guidance of its leader Kim Jong Un.
Kim 'guided the test-fire of (a) new weapon again on Friday morning', the Korean Central News Agency was cited by Yonhap News Agency.
"The national defence scientists showed a perfect result in the test-fire, too, and helped cement bigger confidence in this weapon system."
On Friday, South Korea said that Pyongyang has fired two unidentified projectiles into East Sea.
So far, North Korea has undertaken five projectile test since July 25, likely in a show of protest against the ongoing joint military exercises between Seoul and Washington.
"It is our party's goal of defence building to possess invincible military capabilities no one dares provoke and to keep bolstering them," Kim was quoted as saying.
"Everyone should remember that it is the party's core plan and fixed will for defence building to possess such a powerful force strong enough to discourage any forces from daring to provoke us."
The latest launch came just five days after Pyongyang fired two short-range ballistic missiles.
Meanwhile, United States President Donald Trump has downplayed the testing, outlining that no part of the Singapore agreement was being violated through the launches -- a facet which was referenced in the letter.
Kim also wrote a three-page letter to Trump, in which he expressed his unhappiness over the military drills.
He also offered a 'small' apology for testing the short-range missiles, according to Trump.
Kim reiterated that the testing would stop when the exercises end.