Mortar shells were fired early Monday near the Ground Self-Defense Force camp in the southern Iraqi city of Samawah, police said.
Defense Agency officials in Tokyo said rounds hit several hundred meters west of the camp and added that no GSDF troops were wounded in the incident.
The attack occurred at around 1:40 a.m. and the projectiles were fired from a location 2 or 3 km north of the camp, police said. Witnesses were quoted as saying five explosions were heard in quick succession.
It was not immediately known if any civilians may have been wounded.