The projectiles were fired from its eastern coastal county of Tongchon in Kangwon province earlier in the day, Yonhap News Agency quoted Seoul's Joint Chiefs of Staff (JCS) as saying.
No other details were immediately known, including their type, flight range and maximum altitude.
"Our military is monitoring the situation in case of additional launches while maintaining a readiness posture," the JCS said in a statement.
Friday's launch came six days after North Korea fired two projectiles believed to be short-range ballistic missiles into the East Sea.
It was the sixth such launch since July 25 when it fired two newly developed short-range missiles codenamed KN-23.
Following the launch on Friday, North's Committee for the Peaceful Reunification of the Country issued a statement in which it lashed out at South Korean President Moon Jae-in for his address a day earlier marking Liberation Day from Japan's colonial rule, claiming that his usage of such terms as "worrisome acts" and "provocation" by North Korea is "reckless".
Pyongyang also denounced South Korea's ongoing joint military exercise with the US and the recent announcement of its five-year defence plan, all of which "are aimed at destroying" the North, adding that, "we have nothing to talk any more with the South Korean authorities nor have any idea to sit with them again", Yonhap reported.
North Korea has repeatedly issued warnings against the combined military exercise between South Korea and the US, threatening that it would seek "a new way" rather than engagement if Seoul goes ahead with such a rehearsal for invasion.
In a letter to US President Donald Trump last week, North Korean leader Kim Jong-un also voiced his displeasure over the ongoing exercises that began on Monday.
( With inputs from IANS )