The father of the Boston bombing suspects claims to Channel 4 News that the FBI telephoned his elder son after the attack, and prior to a fatal shootout that claimed the life of a police officer.

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The father of Tamerlan and Dzhokhar Tsarnaev, Anzor, told Channel 4 News that the elder brother had telephoned their mother a few days after the bombings.

Mr Tsarnaev was speaking by telephone to Channel 4 News filmmaker Nick Sturdee (pictured below), who is in Makhachkala, Dagestan. The father said Tamerlan contacted his mother, Zubeidat Tsarnaeva, two or three days after the bombing.

Tamerlan told her the FBI had just rung him and accused him of being behind the attacks, and that he had responded by saying "that's your problem", Mr Tsarnaev claims.

Channel 4 News filmmaker Nick Sturdee spoke to Anzor Tsanaev by telephone

Questions raised

The telephone call claim raises a number of questions.

On the one hand the claim could be false. It follows suggestions by both parents that the FBI had been monitoring Tamerlan for years and could be part of efforts to defend the brothers. Another possiblity is that the telephone call was Tamerlan preparing his mother for bad news.

If the claim is true, then it raises questions over the FBI handling of the investigation into the Boston bombings.

People will be asking about how the alleged telephone call may have fitted into the chain of events - from the attack itself up to the firefight that took place three days later, in which a police officer, as well as Tamerlan, was killed.

The FBI in Boston told Channel 4 News they currently won't confirm or deny any claims about their involvement.

They are waiting to question Dzhokhar Tsarnaev, who is under armed guard in hospital, and reported to be in a serious condition. He was caught in the early hours of Saturday morning.

Boston Mayor Tom Menino said on Sunday that authorities may never be able to question 19-year-old Dzhokhar, who is said to be seriously injured and unable to speak.