LONDON (AFP) - British police investigating the murder of lawmaker Jo Cox said on Friday (June 17) they were focusing on alleged links to far-right groups and reports that her suspected attacker, who remains in custody, was mentally ill.

West Yorkshire Police chief constable Dee Collins said Thursday's brutal attack on the 41-year-old as she went to meet constituents in northern England appeared to be "an isolated, but targeted attack on Jo".

A 52-year-old man, who has been named by British media as local Thomas Mair, was arrested shortly after Cox was shot and stabbed numerous times in the street.

In a statement, Collins said detectives involved in the murder investigation, which is being aided by counter-terrorism specialists, were "keeping an open mind".

"We are aware of the speculation within the media in respect of the suspect's link to mental health services and this is a clear line of enquiry which we are pursuing," she said.

"We are also aware of the inference within the media of the suspect being linked to right-wing extremism which is again a priority line of enquiry which will help us establish the motive for the attack on Jo."

She added: "Based on information available at this time, this appears to be an isolated, but targeted attack upon Jo - there is also no indication at this stage that anyone else was involved in the attack.

"However, we will be investigating how the suspect came to be in possession of an unlawfully held firearm."

Eyewitnesses said that Cox was shot two or three times before being stabbed as she lay on the pavement.

Police confirmed she was attacked with a firearm and a knife after driving up to the library in the village of Birstall for a scheduled meeting with constituents.

A 77-year-old man tried to help her and in turn sustained a "serious injury to his abdomen".

He is currently in a stable condition in hospital, Collins said.

Police have up to 96 hours to question the suspect before they must charge or release him, according to government guidelines for serious crimes such as murder.

London's Metropolitan Police said earlier that Cox had made a complaint about "malicious communications" that resulted in a man being arrested and formally warned by police in March.

Collins said this was one of two unrelated incidents involving "Jo receiving a malicious communication of a sexual nature at her parliamentary office in Westminster".

The second case remains unsolved.