The BBC's Linda Duffin: The reward for information has been increased

Police are to mount a reconstruction on Saturday, a week after the attack, which injured 39 people, including a young boy. They are hoping to jog people's memories in the area.

The reward on offer has been raised to £30,000 following contributions from Lambeth Council and The Voice newspaper.

But almost as soon as the reconstruction was announced the Anti-Nazi League said it planned to hold a demonstration in Brixton on Saturday.

Claire Dissington, of the Anti-Nazi League, says the police should have recognised the attack as "racist" immediately

Arlene Mundle, of the Lambeth Police Consultative Group, urged people stay away from the demonstration which she said would undermine the reconstruction.

On Monday a man claiming to be from the far-right Combat 18 group claimed responsibility for the attack.

But the Metropolitan Police said it was treating the claim with "extreme caution".

One young boy survived a nail embedding in his brain

Three more claims, from individuals claiming to be from far-right groups, came in on Monday but have not been public until now.

'We refuse to fuel their egos'

Detective Chief Superintendent John Bunn said a racist motive was a "very, very serious line of inquiry" but he declined to reveal the identity of those claiming responsibility.

"Giving their names will probably fuel their egos and their twisted minds," he said.

He said "white racist thugs" were most likely responsible but said: "These groups are very small. It's impossible to say whether the claims are real or hoaxes."

Commander Hugh Orde: "We are not ruling out any motive but race is at the top of our agenda"

Detectives have consulted MI5 and other European intelligence agencies who have experience of far-right groups.

Scotland Yard is also investigating the possibility that the bomber may have intended a different target from the market in Electric Avenue.

'Bus could be the key'

Detective Chief Superintendent John Bunn said it was possible whoever planted the devise may have been travelling on a bus that broke down close to the scene of the blast.

The number 159 bus stalled at the market on its way to nearby Streatham.

Mr Bunn said: "We assume a person must have got off that bus and walked towards the explosion before it went off.

Police are still anxious to trace the owner of the sports bag in which the bomb was found

"There is the possibility that the bomber got off that bus and was on his way somewhere else."

Commander Hugh Orde said a full page advert featuring the X-ray of a 23-month old child with a four inch nail in his head was being published in Friday's Evening Standard newspaper.

'Pricking people's conscience'

He said the aim was to "prick the conscience" of anyone with information.

Mr Orde said the black community would no doubt be watching with interest the police's investigation and he said: "We are up to convince them in this case that if this bomb went off in Downing Street, not even one more police officer would be investigating it."

In an apparent reference to the Stephen Lawrence inquiry, he said: "We must recognise our recent history and do everything we can to capture that vital lead."

'Good response from the public'

Detectives received a "good response" to Tuesday's televised appeal on the BBC's Crimewatch UK programme.

But they are still searching for the owner of a black Head sports holdall used in the attack.