North Korea fired an unidentified projectile into the sea off the east coast of the Korean peninsula, according to South Korea's Yonhap news agency, citing South Korea's Joint Chiefs of Staff.
A Joint Chiefs spokesman could not immediately be reached.
Japan's coast guard said North Korea appeared to have fired a missile, which landed outside Japan's exclusive economic zone waters.
North Korea launched multiple projectiles into the sea earlier this month as part of firing drills, according to South Korea's military, drawing US and Chinese appeals for North Korea to return to talks on ending its nuclear and missile programmes.
Earlie state media KCNA said North Korean leader Kim Jong Un guided an an artillery fire competition between combined units of the North Korean army.
North Korea also announced it will hold a session of the Supreme People's Assembly, its legislature, which analysts had said would involve gathering almost 700 of the country's leaders in one spot as the coronavirus spreads worldwide.
"If it goes ahead, it would be the ultimate show of (North Korea’s) confidence in managing the coronavirus situation," Rachel Minyoung Lee, of the North Korea monitoring website NK News, said on Twitter this week.