A test launch of the new ABM interceptor missile for the Moscow missile defense system.
Note how the airframe starts to glow incandescently from aerodynamic heating (we are talking around Mach 10, at an unusually low altitude for such insane speeds), like the US Sprint missile famously did.
Unlike Pavel Podvig I think this was a nominal launch BTW, booster burn time was approximately 4 seconds, which matches earlier videos. More to the point, the disintegration of the first stage after separation due to the immense dynamic pressure on the blunt stage interface was also seen in previous launches. The almost explosive fragmentation isn't always so obvious, but then this is the first video where the event is shown BOTH this close up AND from a lateral perspective. Last but not least, in another parallel between the two missile systems, the Sprint first stage also got ripped apart after it was jettisoned.
Lest people think of 53T6 as a Sprint copy, there are some major differences, most obviously the Russian missile is about twice the size. But it's also single-stage with an un-powered, guided warhead as opposed to the two-stage Sprint, and control is by divert thrusters rather than aerodynamic fins. In these respects 53T6 is more reminiscent of a much enlarged HIBEX.