British police said on Saturday they had charged a man in the slaying of lawmaker Jo Cox, and said the suspect appeared to have acted alone.

West Yorkshire police said on its website that Thomas Mair, 52, had been charged with the murder of the 41-year-old mother of two.

"We have now charged a man with murder, grievous bodily harm, possession of a firearm with intent to commit an indictable offence and possession of an offensive weapon," West Yorkshire Police Detective Superintendent Nick Wallen said in a statement.

Mair was due to appear at Westminster Magistrates' Court on Saturday, Wallen said.

Cox, a supporter of Britain staying in the EU, was shot and stabbed on Thursday by a man who witnesses said shouted "Britain first," in her own electoral district near Leeds in the county of West Yorkshire in northern England.

Wallen said Cox "was attacked and sustained serious injuries from both a firearm and a knife and despite assistance from passers-by, the ambulance service and police officers who were quickly on the scene, she sadly died of her injuries."

Wallen said the suspect was quickly apprehended thanks from help to the public.

He said police, working with the North East Counter Terrorism Unit, was pursuing inquiries into media reports of "the suspect being linked to right wing extremism" and "the suspect's link to mental health services."

"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," Wallen added.

He said, however, that police were working with the Palace of Westminster and the Home Office to review security arrangements for members of parliament.