The projectiles were fired from the North Korean province of Kangwon, according to the South Korean Joint Chiefs of Staff (JCS), which is examining the data collected to try to determine the type of weapon tested.
"Our military is monitoring the situation in case of additional launches while maintaining a readiness posture," the JCS said in a brief release on Friday, Efe news reported.
Friday's launch came six days after North Korea's last such test in which it is believed to have fired two short-range ballistic missiles into the Sea of Japan (known as the East Sea in Korea).
It was the sixth North Korean missile launch since Jul 25, when Pyongyang claimed to have tested two newly developed short-range missiles.
Also Friday, the North's Committee for the Peaceful Reunification of the Country issued a statement targeting South Korea's current joint military maneuvers with the United States, as well as President Moon Jae-in's "foolish" Thursday Liberation Day speech, in which he said he hoped to achieve reunification in 2045, and called for support for the stalled denuclearisation negotiations.
"We have nothing to talk any more with the South Korean authorities nor have any idea to sit with them again," said the statement issued by KCNA, in which the committee said that both the military maneuvers and Seoul's decision to strengthen its radar and anti-missile interceptors "are aimed at destroying the DPRK".
North Korea has repeatedly threatened to seek an alternative to Seoul's mediation if it does not abandon its exercises with Washington, which it considers a threat.