Paranoia

You play as a Russian officer part of the Spetsnaz. You are sent to the Udarnik Industrial Complex on a mission to eliminate the terrorist threats and protect the personnel. However, the game takes a darker turn when the player character (Major Kalashnikov) enters in the abandoned parts of the complex, revealing mutants and zombies alike.

Nearing the end of the game, operatives from presumably the British military, reveal themselves. Earlier, it was revealed the terrorists were actually mercenaries, who were contracted by the British.