The FBI in 2011 interviewed the elder of the two brothers who are suspects in Monday's deadly Boston Marathon bombings, acting at the request of an unidentified foreign government, a US law enforcement source said on Friday.

The FBI's dealings with Tamerlan Tsarnaev - who died overnight in a shootout with police - did not produce any "derogatory" information, and the matter was put "to bed," said the source, speaking on condtion of anonymity.

The revelation is the first indication that Tamerlan Tsarnaev and his younger brother, Dzhokhar, were known to US security officials prior to Monday's bombings, US authorities said