“It is highly likely that poor storage of munitions, left vulnerable to [one-way attack drones], caused a chain reaction of cascading detonations within the bunker system, resulting in enormous losses of ordnance,” the defense ministry wrote in a Saturday intelligence update.

Britain shared multiple satellite images captured on September 19, a day after the attack, showing craters and destroyed storage bunkers at the Toropets arsenal — one of the largest ammunition depots that Russia is using to support its war in Ukraine.

A source in the Security Service of Ukraine told Business Insider after the attack that Russia stored ballistic missiles, bombs, and artillery ammunition at the facility. The source, who spoke on the condition of anonymity to discuss the sensitive operations, said that the warehouse was “literally wiped off the face of the earth.”

Britain’s defense ministry said over 30,000 metric tons of munitions were stored at the facility, including Russia’s highly destructive glide bombs and other ordnance used on the battlefield. Toropets is located more than 300 miles from the Ukrainian border.

Just days after the Toropets attack, over the weekend, Ukraine said it struck two more ammunition depots inside Russia.

The Ukrainian military said it targeted an arsenal in Tikhoretsk, a town in the southern Krasnodar Krai region, that it described as one of Russia’s largest ammunition storage facilities. Kyiv also said it hit another site in the Tver region.

The attacks over the past week mark Ukraine’s latest long-range strikes targeting key military and energy facilities inside Russia.

Ukraine is prohibited from using its Western-provided cruise and ballistic missiles to strike targets inside Russia, so it has relied heavily on domestically produced long-range attack drones to strike high-profile sites like ammunition depots, airbases, and oil refineries.

Britain’s defense ministry said Russia’s air defenses “continue to struggle with Ukrainian deep strike operations,” even though Moscow claimed to have shot down dozens of Ukrainian drones in the Toropets attack.

Conflict analysts have said that Ukraine’s long-range attacks will put Russia’s logistics in a serious bind, and Britain’s defense ministry said that the Toropets attack, specifically, will “highly likely” disrupt Russian ground operations, especially in the Kursk region where Ukrainian forces stunned Moscow by invading last month.