The Russian airbase “Engels-2” has been hit. The base is located 400 km Southeast from Moscow. It hosts strategic bombers of Tu-95 and was the launch pad for numerous attacks against Ukraine.
Russian channels claim it was a drone.
This would change the strategic calculus considerably.
Interesting video of explosion at Engels Airbase. At 15 sec, sound of something passing overhead. At 42 sec, light from explosion. 19 secs later - sound of blast, about 6.2 km away (speed of sound 326.34 m/s, dry air -8 C.)
Video geolocated to here (done myself, others independently established same location). 6.2 km away, in line of sight, is north-eastern part of Engels airbase flight line, where, in this imagery, some Tu-95 bombers are parked.