KYIV (Reuters) - A Ukrainian drone attack destroyed a warehouse storing missiles, guided bombs and artillery ammunition in Russia's Tver region, a source in Ukraine's SBU state security service told Reuters on Wednesday.

The drones caused an "extremely powerful detonation" at a large warehouse of the Main Missile and Artillery Directorate of the Russian Ministry of Defence in the town of Toropets, the source said.

"The warehouse contained missiles intended for Iskander tactical missile systems, Tochka-U tactical missile systems, guided aerial bombs and artillery ammunition," the source said.

After the attack, a fire covered an area six km (3.7 miles) wide, the source added.

Firefighters were trying to contain the fire, the Tver region's governor said, without specifying what was burning.

War bloggers and media reported earlier on Wednesday that a drone attack on Russia had triggered a giant blast and forced the partial evacuation of residents near the site of a large Russian arsenal.

Ukraine's SBU and armed forces continued to "methodically reduce the enemy's missile potential, which it uses to destroy Ukrainian cities," the SBU source said.

Both sides deny attacking civilians in the war fought since Russia's full-scale invasion of Ukraine in February 2022.

(Reporting by Anastasiia Malenko and Tom Balmforth, Editing by Timothy Heritage)