The 26-year-old suspected terrorist, who was killed in a firefight with police in Watertown early Friday morning, traveled to Russia from Boston several times in recent years, according to multiple US officials who have reviewed his passport file - including an extended stay in 2012.

A senior congressional aide privy to the Boston Marathon terror investigation confirmed Saturday that the FBI had been warned about alleged bomber Tamerlan Tsarnaev as far back as 2011, when his apparently suspicious activities prompted Russian authorities keeping close surveillance on militant Islamic groups in the Caucasus region of the former Soviet Union to contact US counterterrorism officials about him.


The alleged bomber's uncle, Alvi Tsarnaev, said in an interview with the Globe that the nephew visited his father in the restive Russian province of Dagestan, which neighbors war-torn Chechnya.

But Alvi Tsarnaev said he did not know who else his nephew may have been involved with while he was overseas.

The apparent alarms sounded about the older of the two suspected bombers two years ago are raising new questions about whether the Marathon attack could have been prevented.

"If the FBI lost track of him, why wasn't he more scrutinized?" asked the congressional aide, who said oversight committees are seeking answer from counter-terrorism officials. "Who was the guy talking to when he went over to Russia? Was he getting training over there?

"The FBI had this guy on the radar and somehow he fell off" the official added, who like the others were not authorized to speak publicly. "We heard for several days leading up to this there was no intelligence. Now we know there could have been intelligence."

The FBI acknowledged Friday night that a foreign government had asked the US for information about Tamerlan Tsarnaev, based on information that he was a follower of "radical Islam." In response, the FBI investigated and interviewed Tamerlan and family members. "The FBI did not find any terrorism activity, domestic or foreign," the bureau said. On Saturday, the FBI said it would have no further comment.


Tsarnaev's brother and alleged co-conspirator in the bombing, Dzhokhar Tsarnaev, 19, was captured by police Friday night in Watertown. He is hospitalized "serious but stable" condition and not yet able to communicate, Governor Deval Patrick told reporters today.

Bryan Bender can be reached at bender@globe.com.