This is all in Russian, but the video speaks for itself…
Essentially the Russian Navy boarded a pirate ship and freed some Russian seafarers who had just been captured by pirates. Then the Russians handcuffed all the pirates to the pirate ship, and blew it up.
***UPDATE***
According to a Telegraph News Report from 2009, the pirates in this video were not, in fact, set on fire and blown up in cold blood by the Russians, but were taken in custody on board the destroyer Admiral Panteleev.