Amid accusations of intelligence failings, officials admit Tamerlan Tsarnaev was on list of known and suspected terrorists

The name of the Boston Marathon bombing suspect was added to a terrorist database by the federal government 18 months before the deadly explosions, it has emerged, adding to pressure on authorities already facing criticism for failing to prevent the deadly attack.

US officials told the Associated Press that Tamerlan Tsarnaev, 26, who was killed in a shootout with the police, was added to a huge classified database of known and suspected terrorists 18 months ago.

The CIA made the request to add his name to the database after the Russian government contacted the agency with concerns that he had become a follower of radical Islam. About six months earlier, the FBI had separately investigated Tsarnaev, also at Russia's request, but the FBI found no ties to terrorism, officials said.

Some US politicians have criticised the failure by the FBI to act earlier. Republican senator Lindsey Graham accused the agency of having "dropped the ball".

Officials say they never found the type of information on Tsarnaev that would have elevated his profile among counterterrorism investigators and placed him on the terror watch list. US intelligence veterans have said accusations of "intelligence failures" after such events are routine and warned that mounting criticism of the FBI risks encouraging future infringements of civil liberties.

Tsarnaev's brother, Dzohkhar, 19, remains in hospital ,where he is recovering from injuries sustained during a getaway attempt. He has told authorities that his older brother only recently recruited him to be part of the attack, two officials said on Wednesday. Dzhokhar has reportedly acknowledged to the FBI his role in the attacks but did so before he was advised of his constitutional rights to keep quiet and seek a lawyer.

Officials said physical evidence, including a 9mm handgun and pieces of a remote-control device commonly used in toys, was recovered from the scene.

Authorities had previously said Dzhokhar exchanged gunfire with them for more than an hour on Friday night before they captured him inside a boat covered by a tarpaulin in a suburban Boston neighbourhood backyard. But two US officials said on Wednesday that he was unarmed when captured, raising questions about the gunfire and how he was injured.

Dzhokhar's public defender declined to comment on the matter. His father has called him a "true angel," and his mother has said she is sure her sons were not involved.

Officials told Associated Press that Tamerlan Tsarnaev was also listed on a homeland security database called the Treasury Enforcement Communications System, or Tecs, that is used to check for terror suspects at the border.

In January and July 2012, when he travelled to Russia and back, the Tecs system sent alerts to the FBI but the agency at that stage had closed its investigation of Tsarnaev because it had not found evidence he was linked to terrorist groups.

A US team of investigators travelled to the Russian province of Dagestan on Tuesday to question the Tsarnaev parents, Anzor Tsarnaev and Zubeidat Tsarnaeva. Officials are investigating Tamerlan Tsarnaev's trip to Russia in 2012 and whether he met extremists during that time. Anzor Tsarnaev and Zubeidat Tsarnaeva told a Russian news agency that they will fly to the United States on Thursday.

On Wednesday, thousands of police officers from across the US gathered at a memorial for the Sean Collier, the 26-year-old Massachusetts Institute of Technology officer, who died after allegedly being shot by the bombing suspects.

© Guardian News and Media 2013