London attacker wasn't linked to al-Qaeda or ISIS, police say

A senior British counterterrorism officer says police have found "no evidence" Westminster attacker Khalid Masood was associated with ISIS or al-Qaeda.

Deputy assistant commissioner Neil Basu said Masood clearly had "an interest in jihad," but police have no evidence he discussed his attack with others.

Basu said in a statement that the attack in which Masood used an SUV and knives to kill four people in London "appears to be based on low-sophistication, low-tech, low-cost techniques copied from other attacks."

Masood was shot dead by police after his deadly rampage, which police have revealed lasted just 82 seconds.

• PHOTOS l Scenes from attack outside British Parliament

Police believe Masood — a 52-year-old Briton with convictions for violence who had spent several years in Saudi Arabia — acted alone, but are trying to determine whether others helped inspire or direct his actions.

Detectives on Monday continued to question a 30-year-old man arrested Sunday and a 58-year-old man arrested shortly after Wednesday's attack. Both were detained in the central England city of Birmingham, where Masood had recently lived.

'I need to know why'

Prime Minister Theresa May said last week that Masood was "a peripheral figure" in an investigation into violent extremism some years ago. But Basu said he was not a "subject of interest" for counterterrorism police or the intelligence services before last week's attack.

Masood was was also known as Adrian Russell Elms or Adrian Russell Ajao, but changed his name in 2005, suggesting a conversion to Islam. 

Basu said there was no sign Masood was radicalized during one of his stints in prison, the last of which was in 2003.

"I know when, where and how Masood committed his atrocities, but now I need to know why," Basu said. "Most importantly, so do the victims and families."

In a statement released by the British Press Association, Masood's mother said that she has shed many tears for those affected by her son's "horrendous" actions.

"I wish to make it absolutely clear, so there can be no doubt, I do not condone his actions nor support the beliefs he held that led to him committing this atrocity," Janet Ajao stated.

As Basu appealed for anyone who spoke to Masood on the day of the attack to come forward, the British government repeated calls for tech companies to give police and intelligence services access to encrypted messages exchanged by terrorism suspects.

Masood used the messaging service WhatsApp just before he began his attack. Home Secretary Amber Rudd said Sunday that such services must not "provide a secret place for terrorists to communicate with each other."

• Khalid Masood reportedly used WhatsApp minutes before London attack

Tech companies have strongly resisted previous calls to create so-called back doors into encrypted messaging, arguing that to do so would compromise the secure communications underpinning everything from shopping to tax returns to online banking.

Rudd is due to hold a previously scheduled meeting with internet companies on Thursday.