South Korea has notified Japan that it plans to conduct a “firing drill” Friday near two tiny disputed outcroppings it controls off Shimane Prefecture, Chief Cabinet Secretary Yoshihide Suga told a news conference Thursday.

The islets are claimed by Japan as Takeshima, but South Korea calls them Dokdo. The fire zone overlaps an area Japan claims as its territorial waters.

South Korea did not say what weapons will be used during the drill, a Japan Coast Guard spokesman said.

Japanese diplomats in Seoul have already asked South Korea to cancel the exercise, Suga said. The drill is reportedly to be conducted from 9 a.m. to 5 p.m.

“Given our position on the sovereign right of Takeshima, we cannot accept” the exercise, Suga said.

The Japan Coast Guard issued a warning to Japanese ships not to enter the fire zone, which is southwest of the islets and stretches about 150 km east to west and 55 km north to south.