The 69-year-old was attacked at Belfairs Methodist Church while holding one of his regular constituency surgeries. A knifeman is understood to have walked into the church in the Southend area of Essex before carrying out the vicious assault.
Police have confirmed he tragically passed away at the scene.
One man has been arrested and a knife has been recovered from the scene.
Eastwood Road North in Leigh-on-sea has been closed between Bellhouse Lane and Oakwood Avenue while police respond to the attack.
In a statement Essex Police said: "A man has been arrested on suspicion murder after a man was stabbed in Leigh-on-Sea.
"Let us remember him and what he did with his life."
Labour's deputy leader, Angela Rayner said: "I'm horrified by the reports regarding David Amess and an incident at his constituency surgery today.
The attack comes five years after Labour MP Jo Cox was horrifically murdered in a knife attack while in her constituency in 2016.
Following the assault on Sir David, the foundation set up in Jo Cox's name said: "The Jo Cox Foundation is horrified to hear the news of the attack on Sir David Amess MP.
"We are thinking of him, his family and loved ones at this distressing time."
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