The Moscow theater hostage crisis, also known as the 2002 Nord-Ost siege, was the seizure of a crowded Moscow theatre on October 23, 2002 by about 40-50 armed Chechen rebel fighters who claimed allegiance to the separatist movement in Chechnya. They took 850 hostages and demanded the withdrawal of Russian forces from Chechnya. The siege was led by Movsar Barayev (age 22). After a two-and-a-half day siege, Russian special forces pumped an unknown chemical agent into the building's ventilation system and violently raided it. Officially, 39 of the terrorists were killed by Russian forces, along with at least 129 of the hostages. All but two of the hostages who died during the siege were killed by the toxic substance pumped into the theatre to subdue the militants.