Investigators are exploring potential links between Boston Marathon bombing suspect Tamerlan Tsarnaev and an extremist group known as the Caucasus Emirate, sources tell Fox News.
The purported leader of the separatist and Islamic extremist group is Doku Umarov, a Chechen Islamic militant in Russia whose ordering of numerous attacks on civilians has earned him the nickname Russia's Usama bin Laden.  The U.N.'s Al Qaeda sanctions committee has also cited Umarov for his alleged connections with Al Qaeda and other extremist groups.
The investigation is based on the contents of Tsarnaev's YouTube channel and his trip to Russia in the first half of 2012, which included stops in Dagestan and Chechnya.
Sources tell Fox that videos deleted from his YouTube account include a “terrorist playlist” and links to Vilayat Dagestan, which is associated with Caucasus Emirate.
The 26-year-old Tsarnaev was killed early Friday in a shootout with police. His 19-year-old brother, Dzhokhar Tsarnaev, was captured that night. They are suspected of placing two bombs along the marathon course Monday that killed three and injured roughly 180 others.
Investigators are now looking for potential ties including Tamerlan’s email traffic, the posting of videos in support of an Islamist objective and whether there was person-to-person contact.
Sources tell Fox that Caucasus Emirate is one of several groups being investigated.
Caucasus Emirate was designated a foreign terrorist organization by the State Department in 2011.
“The group uses bombings, shootings and attempted assassinations to provoke a revolution and expel the Russian government from the North Caucasus region,” according to designation.
Ambassador Daniel Benjamin, the department’s coordinator for counter terrorism, said the designation was in response to “threats posed to the United States and Russia.”
“The attacks perpetrated by Caucasus Emirate illustrate the global nature of the terrorist problem we face today,” he also said.  “We stand in solidarity with the Russian people in our condemnation of these deplorable terrorist acts.”
Caucasus Emirate was also listed in March 2011 by the United Nations’ Al Qaeda and Taliban Sanctions Committee.