Police investigating the Westminster attack said on Monday that they have found no evidence that killer Khalid Masood had any links with radical Islamist groups such as ISIS or Al Qaeda.
In a briefing at New Scotland Yard, Deputy Assistant Commissioner Neil Basu, senior national coordinator for UK Counter Terrorism Policing, said there was also no evidence that Masood had been radicalised while serving a jail term in a British prison, Xinhua news agency reported.
Basu said there has been much speculation about who Masood was in contact with prior to the attack last week which left four people, including a London police officer dead, and dozens more injured. Masood was shot dead by police at the Houses of Parliament.
Basu added: "Masood's communications that day are a main line of enquiry. If you heard from him on March 22, please come forward now, the information you have may prove important to establishing his state of mind.
"His attack method appears to be based on low sophistication, low tech, low cost techniques copied from other attacks, and echo the rhetoric of IS leaders in terms of methodology and attacking police and civilians, but at this stage I have no evidence he discussed this with others.
"There is no evidence that Masood was radicalised in prison in 2003, as has been suggested; this is pure speculation at this time. Whilst I have found no evidence of an association with IS (the Islamic State) or AQ (Al Qaeda), there is clearly an interest in jihad."
Basu repeated the request to the public for their help, specifically to those who knew or talked to Masood in the months, weeks and days leading up to the attack.
"We are tracing these people, but I would ask you all to voluntarily come forward and help our investigation," said Basu.
Police said the attacker changed his name to Khalid Masood in 2005.
"His last criminal offence was 2003 and he was not a current subject of interest or part of the current domestic or international threat picture for either the security service or Counter Terrorism Policing.
"I know when, where and how Masood committed his atrocities, but now I need to know why. Most importantly, so do the victims and families," added Basu.
On last Wednesday, Khalid Masood, 52, drove a car through crowds of pedestrians on Westminster Bridge, killing three: Aysha Frade, a 43-year-old British national of Spanish origin, Kurt Cochran, an American tourist whose wife was injured in the attack, and Leslie Rhodes.
A police officer was also fatally stabbed by Masood, who was later shot dead by police.
(With IANS inputs)