LONDON - One of the three suspected attackers in the London Bridge terror attack was reported to police two years ago, British media reports said, raising questions over whether the suspect might have slipped through Britain's intelligence network.

Seven people were killed when the three knife-wielding men mowed down pedestrians on London Bridge before going on a stabbing spree at the nearby Borough Market on Saturday evening.

The BBC on Monday reported police as saying they were aware of the identity of the three attackers, but would not be releasing details about them at this stage.

The Daily Mail reported on Monday (June 5) that one of the attackers was a 27-year-old Muslim extremist who was previously seen in a TV documentary last year about British extremists.

He had appeared alongside two notorious preachers who were known to police and intelligence officials. The paper also said that the man was involved in an altercation with police after they brought out an ISIS flag and unfurled it in a park.

According to the paper, a friend of the attacker also reported him to an anti-terror hotline after he became radicalised through watching extremist YouTube videos.

Police had also been warned after the suspect reportedly attempted to radicalise children in a local park, The Daily Mail and The Guardian reported.

Italian Erica Gasparri, who lives in the same complex as the attacker, said he was a "Pakistani man" known locally as "Abs". The mother of three said she confronted him at the park two years ago after her son came home one day and told her he wanted to be a Muslim.

According to Gasparri, the man said he was "ready to do whatever I need to do in the name of Allah". She said he told her he was "ready in the name of Allah to do what needs to be done, including killing my own mother."

"He would go down to the park and talk to them about Islam and he also came to the houses and gave the kids money and sweets during Ramadan," she told The Guardian.

Gasparri said she took photographs of the man and gave them to the police. She said the information was passed on to Scotland Yard, the police headquarters, but no one followed up with her.

"That was two years ago. No one came to me. If they did, this could have been prevented and lives could have been saved," she said.

Neighbours of the suspect told The Mirror they were shocked by the attack, adding that he appeared quiet and unassuming.

The residents who are living in King Road in the suburban town of Barking, east London, were awoken on Monday by armed police raiding a block of flats in connection with the attack.

Construction worker Seva Litvjakovs, who lives in the block that was raided, recognised the attacker from a picture of the attack posted on Twitter, where the suspect appeared to be wearing an Arsenal shirt.

Litvjakovs, 35, said: "I looked on Twitter and saw one of the terrorists who had been shot by police and he looked 90 per cent like my neighbour - he was even wearing the same Arsenal shirt that I had seen him in at 5pm that evening." "I only had a normal neighbour relationship with him, but he always smiled and said 'hello.'"