Conservative MP Sir David Amess has died after being stabbed multiple times at his constituency surgery in Essex.
Police said a 25-year-old man was arrested on suspicion of murder after the attack at a church in Leigh-on-Sea.
They recovered a knife and are not looking for anyone else in connection with the incident. A counter terrorism team will lead the investigation.
Boris Johnson has spoken of his shock and sadness at the loss of “one of the kindest” people in politics.
Home Secretary Priti Patel has asked all police forces to review security arrangements for MPs “with immediate effect”, a Home Office spokesman said.
Sir David, 69, had been an MP since 1983 and was married with five children. He is the second serving MP to be killed in the past five years, following the murder of Labour MP Jo Cox in 2016.
She was killed outside a library in Birstall, West Yorkshire, where she was due to hold a constituency surgery.
The investigation into the attack will be led by the Metropolitan Police’s specialist Counter Terrorism Command, who will determine whether it was a terrorist incident.
The prime minister said Sir David had an “outstanding record of passing laws to help the most vulnerable”.
“David was a man who believed passionately in this country and in its future. We’ve lost today a fine public servant and a much-loved friend and colleague,” said Mr Johnson.
Ms Patel said the killing “represents a senseless attack on democracy itself”, adding that “questions are rightly being asked about the safety of our country’s elected representatives”.
Sir David, who represented Southend West, was holding a constituency surgery – where voters can meet their MP and discuss concerns – at Belfairs Methodist Church in Eastwood Road North.
Essex Police Chief Constable Ben-Julian Harrington said they received reports of a stabbing shortly after 12:05 BST and within minutes, officers found Sir David with multiple injuries.
Police and paramedics “worked extremely hard” to save him but he died at the scene, Mr Harrington said.
Police have appealed for anyone who saw the attack, or who has footage from CCTV, dash cams or video doorbell to contact them.
Southend councillor John Lamb told the BBC that Sir David moved his surgeries to different locations around the constituency “to meet the people” and said the attack was “absolutely dreadful”.
“We’ve lost a very good, hard-working constituency MP who worked for everyone,” he said.
Source: BBC.com