Ambulances are seen outside the Houses of Parliament in London, Britain on March 22, 2017. (Xinhua/Tim Ireland)

LONDON, March 27 (Xinhua) -- There was no evidence the Westminster assailant Khalid Masood had any links with the extremist group Islamic State (IS), the police in London said on Monday night.

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 radicalized while serving a sentence in a British prison.

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 armed police at the Houses of Parliament.

The senior police chief said: "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, but at this stage I have no evidence he discussed this with others."

" Whilst I have found no evidence of an association with IS or AQ (Al-Qaida), there is clearly an interest in jihad," added Basu.

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 in 2005 the attacker changed his name to Khalid Masood.

"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," said Basu.