Social media users are being warned of a hoax scam which spreads fake terror news to trick victims into disclosing their Facebook details.

Lawyers for Boston Marathon bombing suspect Dzhokhar Tsarnaev have asked a judge to make prosecutors turn over family-related evidence as they try to build a case that his older brother was the “main instigator” of the deadly attack.

The net was last night closing in on at least one individual believed to be responsible for the Boston Marathon bombings which claimed the lives of three people and injured 176 others in the worst attack on US soil since 9/11.

Investigators have an image of a potential suspect in the deadly Boston Marathon bombing but do not know his name and have not questioned him, a law enforcement official said today.

FBI agents zeroed in on how the Boston Marathon bombing was carried out – with kitchen pressure cookers packed with explosives, nails and other lethal shrapnel - but said they still did not know who did it and why.