British police said on Saturday they had charged a 52-year-old man in the slaying of lawmaker Jo Cox, and said the suspect appeared to have acted alone.
Cox, a supporter of Britain staying in the European Union, 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.
Her murder has left Britain in shock and campaigning for next week's referendum on whether to remain in the EU has been suspended as a mark of respect.
West Yorkshire police said on its website that Thomas Mair had been charged with the murder of the 41-year-old mother of two and was due to appear at Westminster Magistrates' Court later on Saturday.
Police, working with the North East Counter Terrorism Unit, were pursuing inquiries into media reports of "the suspect being linked to right wing extremism" and "the suspect's link to mental health services," West Yorkshire Police Detective Superintendent Nick Wallen said in a statement.
"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 said.
Mair had been charged with murder, grievous bodily harm, possession of a firearm with intent to commit an indictable offence and possession of an offensive weapon, police said.
Police have said counter-terrorism officers are also involved in the investigation into the attack, which occurred as Cox arrived for a meeting with constituents.
The murder has sparked debate in Britain, which has strict gun controls, about the safety of lawmakers, the heightened tempo of political confrontation and whether the slaying would affect the outcome of the referendum.
Wallen said police were working with the Palace of Westminster and the Home Office to review security arrangements for members of parliament.
The killing prompted a suspension of campaigning for the June 23 EU referendum, the tone of which has become ugly and included bitter personal recriminations as well as furious debate of issues such as immigration and the economy.
Prime Minister David Cameron has agreed to recall parliament on Monday in tribute to Cox, who was considered an outstanding member of the new intake of Labour parliamentarians. She had been a prominent aid worker.
Both sides have put their national EU campaigns on hold until at least Sunday.