* House to hold hearing into Tamerlan Tsarnaev tip
* Questions about lack of cooperation from Russia (New throughout with comments, House briefing)
By Patricia Zengerle
WASHINGTON, April 22 (Reuters) - U.S. lawmakers will question senior security officials this week about whether the FBI mishandled information on one of the Boston bombing suspects who was flagged by Russia two years ago as a possible Islamist radical.
Top investigators will brief the full House of Representatives on Tuesday about the failure to spot the danger from Tamerlan Tsarnaev, one of two ethnic Chechen brothers suspected of carrying out the Boston Marathon bombings, which killed three people and injured more than 200.
Some lawmakers have accused the FBI of failing to act thoroughly enough after Russia's security services raised concerns about Tamerlan Tsarnaev in 2011.
"We're going to have to sort it out," said Democratic Senator Dianne Feinstein, who chairs the Senate Intelligence Committee, which will be briefed on the case during a closed hearing on Tuesday. She declined further comment.
The full Senate is expected to receive a briefing from intelligence officials later in the week, aides said.
Lawmakers want to know why the FBI discounted the older Tsarnaev brother as a possible threat after interviewing him in 2011. The following year, he flew to Russia and visited the southern regions of Dagestan and Chechnya, where Islamist militants are active.
The 26-year-old died in a gunfight with police early on Friday. His younger brother Dzhokhar Tsarnaev, 19, was charged in a Boston hospital on Monday with using a weapon of mass destruction and malicious destruction of property resulting in death in connection with the bombings.
Republican Senator Lindsey Graham, who accused the FBI on Sunday of "dropping the ball" on the elder Tsarnaev, was less critical in comments on Monday.
He said he had spoken to the FBI, which explained that Moscow did not reply to later U.S. requests for more information about the suspect.
"This is an example of where we need better cooperation," Graham told a news conference. "They indicated to us that they never received any input from the Russians after the 2011 inquiry," said Graham, a member of the Senate Armed Services Committee.
He questioned why Tamerlan Tsarnaev's online connections to radical websites did not cause the FBI to identify him as a potential threat and suggested that the country may need to alter privacy laws to allow closer tracking of online activity. (Reporting by Patricia Zengerle; Additional reporting by Susan Cornwell; Editing by Alistair Bell and Eric Beech)