MOSCOW (AP) — A drone-borne explosive device detonated Sunday at the headquarters of Russia's Black Sea Fleet, injuring six people, officials said.

The explosion at the headquarters in the city of Sevastopol on the Crimean peninsula that Russia annexed from Ukraine in 2014 caused cancellation of observances of Russia's Navy Day holiday.

The Black Sea Fleet's press service said the drone appeared to be homemade. It described the explosive device as “low-power” but Sevastopol mayor Mikhail Razvozhaev said six people were injured in the blast.

There was no immediate information on where the drone began its flight.