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.