WASHINGTON (AFP, AP) - United States President Barack Obama on Tuesday defended the Federal Bureau of Investigation (FBI) from suggestions it might have prevented the Boston marathon bombing by acting on warnings about one of the suspects.

Russia had warned the US authorities about ethnic Chechen Tamerlan Tsarnaev in 2011 and the possibility he was slipping into the grips of hardline Islam, and the FBI probed and interviewed him, although he went on to carry out the bombing.

Mr Obama said the US authorities had done the best they could in the face of threats that include what he called "self-radicalised individuals".

"Based on what I've seen so far, the FBI performed its duties. The Department of Homeland Security did what it is was supposed to be doing. But this is hard stuff," he said, adding that Russia had been very cooperative in the post-bombing probe.

Still, he acknowledged lingering suspicions between the intelligence and law enforcement agencies of the two former Cold War foes.

"You know, old habits die hard," Mr Obama said.

Tamerlan and his younger brother Dzhokhar are accused of going on to carry out the April 15 bombing, which killed three and wounded more than 264 at one of the world's premier sporting events.

Tamerlan died in a shootout with police as he tried to flee the Boston area three days after the bombing. His younger brother was wounded and captured.

Mr Obama said a national security review will look at whether there is more the government can do to stop people within the US who might become radicalised and plan terror attacks.

One of the dangers the US faces now, he said, is people who might decide to attack because of "whatever warped, twisted ideas they may have".

The top US intelligence official, meanwhile, is reviewing how sensitive information was shared before the deadly Boston Marathon bombings to determine whether anything was missed that could have stopped the suspects blamed for the attacks.

Director of National Intelligence (DNI) James Clapper agreed to the review by the Intelligence Community Inspector General across the 16 intelligence agencies. Lawmakers have suggested that an intelligence breakdown may have contributed to the attacks.

DNI spokesman Shawn Turner said Mr Clapper believes his agencies shared information appropriately.

Mr Turner said the review is limited to the handling of information related to the suspects prior to the attack.

The review was first reported by The Boston Globe newspaper.