An Islamist group from Russia's North Caucasus has threatened to attack the Sochi Winter Olympics in a video published online.
In a warning to President Vladimir Putin over next month's Games, the hosts and visitors were singled out for target: "If you hold the Olympics you will receive a present from us... for you and all those tourists who will come over.
"It will be for all the Muslim blood that is shed every day around the world - be it in Afghanistan, Somalia, Syria, all around the world. This will be our revenge."
The video says two men from the group Vilayat Dagestan, linked to an Iraqi faction called Ansar al-Sunna carried out the two attacks in Volgograd last month that killed 34 people and injured more than 100.
Dagestan, in Russia's North Caucasus, has seen years of fighting between the Russian army and Muslim groups seeking independence.
Responding with a massive counter-insurgency operation, Moscow has been accused of heavy-handed tactics and using collective punishment to quash uprisings.
Rebel leader Doku Umarov has urged fighters to attack the Games in Sochi, which lies on the western edge of the Caucasus mountains.
Implementing stringent security measures in the southern resort of Sochi, tens of thousands of Russian police, security agents, rescue workers and soldiers have been deployed for the games.
Putin has staked much personal and political prestige on the Games, which are intended to show how far Russia has come since the collapse of the Soviet Union in 1991.