Tamerlan Tsarnaev, one of the two brothers accused of orchestrating the Boston marathon bombings, entered into the radar of Russia's inteligence officers in 2011 when he mentioned "jihad" in a phone call with his mother, a law enforcement official in the United States told the New York Times.

In 2011, Russia asked the FBI for information about Tamerlan Tsarnaev who had lived for about a decade in the United states. The request stated that it was based on information that he was a follower of radical Islam and a strong believer, and that he had changed drastically since 2010 as he prepared to leave the United States for travel to Russia's region to join unspecified underground groups.

The FBI reviewed Tamerlan's communications and online activity and interviewed him and family members, but it did not find any terrorism activity, domestic or foreign.

The latest report on the matter that surfaced on Saturday, states that the warnings from Russian officials were based on two intercepted telephone calls discussing "jihad," according to a U.S. law enforcement official who spoke to the Times. Jihad is a word that is commonly associated with "Holy War." 

Tamerlan however did not mention specific attack plans in the phone calls, the U.S. official said.

Both calls involved Tamerlan's mother Zubeidat Tsarnaeva and his brother Dzhokhar. One of the calls was between Tamerlan and his mother and the other was between his mother and another person in Russia that is currently being investigated by the F.B.I., according to reports.

The official source told the Times, that it wasn't until recently that Russia unveiled the reasons behind their warning two years ago.

The bombers' mother has spoken to media outlets denying that her children plotted and carried out the attacks and has even said that the injuries were staged.

"Impossible for both of them to do that... its set up. He would never hide it from me. My youngest son was raised in America and my old son never told me he was on the side of jihad." 

She has also spoken to the press about coming to the U.S. and said she is still thinking about it because she fears she could be arrested after she was charged with stealing clothes from a shop.