A British Member of Parliament (MP) for Southend West in Essex, Sir David Amess was stabbed on Friday afternoon during a constituency surgery at Belfairs Methodist Church in Leigh-on-Sea.
Police officers and paramedics tried to save him but he died at the scene.
The Metropolitan Police said that the early investigation had revealed “a potential motivation linked to Islamist extremism”.
A 25-year-old man – understood to be a Briton with Somali heritage – was arrested immediately at the scene on suspicion of murder and remains in custody.
Sir David Amess a father-of-five had been an MP for 38 years, and while he never held a ministerial role, he was known as someone who took on the causes of his constituents.
The 69-year-old David Amess who was a life long Conservative party member is the second MP killed in their own constituency in little more than five years, following the 2016 murder of Labour’s Jo Cox.
Home Secretary Priti Patel has asked all police forces to immediately review security arrangements for MPs, while House of Commons Speaker Sir Lindsay Hoyle has also pledged to “examine” safety measures.