Factbox-What do we know about the Ukrainian attack in Russia’s Tver region?

(Reuters) – A major Ukrainian drone attack on Russia triggered a giant blast and forced the partial evacuation of residents near the site of a large Russian arsenal in the Tver region on Wednesday, war bloggers and some media reported.

What do we know so far?

* The attack sparked giant blasts and a blaze in Toropets, a 1,000-year-old town, which has a population of just over 11,000, about 250 miles (400 km) west of Moscow.

Fire fighters were trying to contain the fire, Igor Rudenya, the governor of the Tver region, said in a post on the Telegram messaging channel of the region’s administration. He did not say what was burning.

* Unverified video and images on social media showed a huge ball of flame blasting high into the night sky and detonations thundering across a lake in the region that lies northwest of Moscow and not far from the border with Belarus.

* NASA satellites picked up multiple heat sources emanating from the site in early Wednesday hours and earthquake monitoring stations picked up what sensors thought was a minor earthquake in the area.

* According to a RIA state news agency report from 2018, Russia was building an arsenal for the storage of missiles, ammunition and explosives in Toropets. The arsenal was built in 2015 at a cost of 3.6 billion roubles ($39 million), according to Rossiyskaya Gazeta, the Russian government’s official newspaper.

* It is equipped with cold and heated rooms, electrical substations, treatment facilities, water and fuel storage tanks, and more than a hundred fire ponds, Rossiyskaya Gazeta said. The arsenal was put into operation in 2018, then-deputy defence minister Dmitry Bulgakov told RIA. Bulgakov was arrested earlier this year on corruption charges. He denies the charges.

* Bulgakov said in 2018 that the arsenal is equipped with concrete storage facilities for storing missiles, ammunition and explosives in the proper conditions, RIA reported.

“It (the concrete facilities) ensures their reliable and safe storage, protects them from air and missile strikes and even from the damaging factors of a nuclear explosion”, RIA quoted Bulgakov as saying.

* Bulgakov told Russian army news outlet Zvezda in 2018 that the full load of each storage facility of the arsenal is up to 240 tons. The arsenal also has facilities to accommodate up to 200 servicemen, the RIA report says.

($1 = 91.4000 roubles)