British Prime Minister Boris Johnson said his heart was filled with "shock" and "sadness" on Friday night, in his first statement following the murder of Conservative member of parliament Sir David Amess.
Johnson said Amess was one of the "most gentle" and "kindest" people in British politics, in a video statement that appeared on local media.
"David was a man who believed passionately in this country and its future," he said.
"We've lost today a fine public servant and a much-loved friend and colleague."
Johnson said: "I think everybody was deeply shocked and heart-stricken," adding that his thoughts were with Sir David's wife and children.
Home Secretary Priti Patel tweeted that "questions are being asked about the safety" of parliamentarians following Sir David Amess' death.
Patel said she would provide updates "in due course," adding that she was "devastated" and saw Sir David as a "kind and loyal friend."
Amess was killed in a knife attack on Friday as he was meeting with his constituents in a church in Leigh-on-Sea.
Essex police said a 25-year-old man was arrested on suspicion of murder after confirming the identity of the victim.
"We are now in a position to sadly confirm the man who died in Leigh-on-Sea today was Sir David Amess MP," the force tweeted.