North Korea has fired two unidentified "projectiles" into the sea, the South Korean military says.
According to Japan's Defence Ministry, the objects "appeared to be ballistic missiles".
If confirmed as a missile test, it would be the North's 12th such launch this year.
Earlier this month, North Korea test-fired a new type of missile which is thought could also be launched from a submarine.
That missile was, in theory, able to carry a nuclear weapon. Being launched from a submarine can make missiles harder to detect, and allows them to get closer to other targets.
Thursday's projectiles were fired into the East Sea, also known as the Sea of Japan. The launches are thought to have come from South Pyongan province, according to Seoul's Joint Chiefs of Staff.
The projectiles landed outside Japan's maritime exclusive economic zone, the Japanese coast guard said.
The South Korean military said it would maintain its readiness to track and monitor further launches.
The launch coincided with the day South Korean President Moon Jae-in attended the funeral of his mother, who died earlier this week.
On Wednesday, North Korean leader Kim Jong-un had expressed "deep condolences" and "consolation" to Mr Moon.
North Korea is widely believed to have missiles capable of striking long-range targets, including the US mainland.
It also claims to have a nuclear bomb it can mount it on a missile.
The apparent testing comes as nuclear talks between Pyongyang and Washington remain at a deadlock.
The last time US President Donald Trump met the North's Kim Jong-un was in June, when the two leaders met at the inter-Korean border.
Talks between US and North Korean officials in Sweden earlier this month failed to make any progress.