Russian special forces killed two members of a jihadist group in an early morning raid this weekend in the semiautonomous republic of Dagestan, two Russian police sources told CNN on Monday.
Authorities have not said the raid Sunday had anything to do with the Boston Marathon bombing.
But one of those killed was an associate of Abu Dujan, the slain leader of a militant Islamist organization that produced at least one video that slain bombing suspect Tamerlan Tsarnaev apparently posted and later removed from a social media account, according to an analysis by CNN and the SITE Intelligence Group.
Videos linked to the group show how to make homemade explosive devices, among other things.
U.S. investigators have been looking into whether Tsarnaev could have been influenced by such groups during his six-month visit to the region in 2012.
The interplay between U.S. officials and their counterparts in Russia -- who have been battling Islamist militants in the region for years -- has emerged as a key thread in discussions of the April 15 Boston bombing, which killed three and left more than 260 wounded. Authorities say that Tsarnaev and his younger brother, Dzhokhar Tsarnaev, also shot a police officer to death.
Tamerlan Tsarnaev died after a gun battle with police early April 19 in Watertown, Massachusetts, that injured his younger brother, who was later captured.
Over the weekend, an official with knowledge of the investigation told CNN that Russian authorities had intercepted a phone call in early 2011 from one of the Tsarnaev brothers in the U.S. to their mother in Dagestan.
The wiretapped communication discussed jihad, but the conversation was vague, two U.S. officials said. It's unclear why the Russians were eavesdropping on the mother or for how long.
CNN has previously reported that the FBI conducted an investigation -- including an interview with Tamerlan Tsarnaev -- after Russia expressed concerns in 2011.
The Russians also raised questions about Tsarnaev's mother, Zubeidat Tsarnaev, according to several sources. Her name was subsequently added to a terrorism database along with her son's, an intelligence official said last week.
The FBI said at the time that it found nothing to justify further investigation and that Russia did not respond to U.S. requests for more information. The case was closed after several months.
One of the officials declined to say whether the information from the wiretapped phone call would have made a difference in uncovering plans for a future attack on the U.S.
However, CNN contributor Tom Fuentes said the FBI would have found that information helpful after Russian officials asked the agency to look at Tamerlan Tsarnaev for signs of a possible shift toward increasing Islamic extremism.
On Monday, Zubeidat Tsarnaev told CNN's Nick Paton Walsh that she plans to come to the United States if she can see her son, despite pending shoplifting charges against her in Massachusetts.
The 19-year-old suspect is now at Federal Medical Center Devens, about 40 miles west of Boston. Authorities moved him there last week from Boston's Beth Israel Deaconess Medical Center.
He had what appeared to be gunshot wounds to his head, neck, legs and hand when he was captured on April 19 after a nearly 24-hour manhunt, according to the criminal complaint accusing him in the marathon blasts.
He is able to speak and has been interacting with staff, a prison spokesman said.
He has, however, apparently been less talkative since authorities read him his Miranda rights three days after his capture.
But the information gained from two sessions of questioning has produced good leads, a U.S. law enforcement official said. He has been charged with using a weapon of mass destruction.
In other developments over the weekend:
-- Attorney General Eric Holder told reporters that he was comfortable with the handling of the initial questioning of Dzhokhar Tsarnaev at a Boston hospital. A magistrate's decision to read him his constitutional rights was "totally consistent with the laws that we have," Holder said. "We have a two-day period to question him under the 'public safety' exception. So I think everything was done appropriately, and we got good leads."
-- Authorities have finished combing a New Beford, Massachusetts, landfill for clues that may shed light on the bloody attack, said FBI spokeswoman Laura Eimiller. She wouldn't say whether investigators turned up anything. A law enforcement official with knowledge of the investigation had said investigators were looking for Dzhokhar Tsarnaev's laptop computer. Tsarnaev led authorities to look there, the source said, and others who may have knowledge of the computer's whereabouts, or who may have played a role in disposing of it, also provided leads that prompted the search.
-- The boat where Tsarnaev was captured in the backyard of a Watertown, Massachusetts, home has been taken to an undisclosed location to be thoroughly examined, according to the FBI.
-- CNN's Ashleigh Banfield, Paula Newton, Drew Griffin, Dave Alsup, Carol Cratty, Brian Todd and Barbara Starr contributed to this report.
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