Four Russian embassy workers taken hostage in Iraq have been killed, according to a statement posted on the Internet. The staff were kidnapped when gunmen blocked their vehicle in Bahgdad on June 3. A fifth man was killed in the attack.An Iraqi al Qaeda-led group had demanded that Russia withdraw its troops from Chechnya and release all Muslim prisoners. It said last week that it had decided to kill the Russians after Moscow failed to meet its demands. The Web posting showed video footage of the killing of two men it said were Russian captives and the beheaded body of a third man.