Seoul said Kyiv's public disclosure of the repatriation of two North Korean prisoners endangered their families in North Korea, where relatives of those who fall into enemy hands face punishment. Ukraine has rejected South Korea's accusations.
Japan's military said the missile landed in waters outside its exclusive economic zone, while South Korea's military, which often accuses the North of exaggerating its capabilities, said it travelled more than 700 kilometres.
The POWs were captured by Ukrainian forces early last year after being deployed alongside thousands of North Korean troops to support Russia's war against Ukraine.
North Korea in recent years has added mines, anti-tank barriers and other front-line fortifications, raising concerns in the South about the growing presence of North Korean soldiers near the border.
The northern and southern boundaries of the zone are among the world's most heavily fortified frontiers, and landmine incidents have previously heightened tensions between the two Koreas.
North Korean soldiers were among the foreign contingent conscripted to fight alongside Russian troops on various frontlines in the war on Ukraine, after the Kremlin sought assistance from its close allies to bolster its deployments amid struggles with domestic conscription.