Sergeant Graham Saville, 46, was left in a critical condition following the incident on Thursday.
He died on Tuesday afternoon with his family at his bedside, Nottinghamshire Police confirmed.
A spokesperson said his death in the line of duty sent “shockwaves and sadness” through the force, and paid tribute to the “service and sacrifice” of the “hugely respected and popular” officer.
Police were deployed to a residential area near Newark Northgate station around 7pm on Thursday, following concerns over the welfare of a man on the tracks.
Sgt Saville, a Nottinghamshire Police officer based at Newark Police Station, was hit by a train as he tried to rescue the man, and sustained serious injuries.
He was taken to Queen’s Medical Centre in Nottingham, where he died on Tuesday afternoon “with his family by his side”, British Transport Police (BTP) said.
Announcement | Death of Sergeant Graham Saville
It is with great sadness that Nottinghamshire Police confirms the death of a serving officer in the line of duty.https://t.co/rLm7fvBUS5
— Nottinghamshire Police (@nottspolice) August 29, 2023
Nottinghamshire Police Chief Constable Kate Meynell said on Tuesday: “Today is a day of mourning for the entire police family.
“Graham was a hugely respected and popular colleague and his death in the line of duty has come as an enormous shock to us all.
“Our hearts and deepest condolences go out to his family and we will do everything we can to support them through this unimaginably devastating time.
“It is impossible to put into words how devastating this news is for everyone who loved and respected Graham.
“On Thursday, he went to work to protect the people of Nottinghamshire from harm, and it is testament to his bravery and dedication as a police officer that he was fatally injured while attempting to save another man’s life.
“His service and sacrifice will never be forgotten.
“I would also like to pay tribute to the officers who attended the scene, some of whom provided immediate medical assistance while the ambulance was on its way.
“This was a deeply traumatic incident for those officers and we have a dedicated team providing support to them.
“When a colleague dies in the line of duty the shockwaves and sadness reverberate throughout the policing family and we will all deeply mourn our colleague.”
Home Secretary Suella Braverman wrote on social media: “I offer my deepest condolences to the family and @nottspolice colleagues of Sergeant Graham Saville, who has lost his life after saving a man in distress on a railway line. We owe our police officers an immense debt of gratitude for their bravery while protecting us all.”
Policing minister Chris Philp posted on X, previously known as Twitter: “I’m deeply saddened to learn of the passing of Sgt Graham Saville, following his brave work to save someone else’s life on a railway line. He selflessly made the ultimate sacrifice. We will remember him. Our thoughts are with Graham’s family & colleagues”
I offer my deepest condolences to the family and @nottspolice colleagues of Sergeant Graham Saville, who has lost his life after saving a man in distress on a railway line.
We owe our police officers an immense debt of gratitude for their bravery while protecting us all. https://t.co/hBcCxA09RQ
— Suella Braverman MP (@SuellaBraverman) August 29, 2023
Nottinghamshire Police was set to fly flags at half-mast as a mark of respect, following Sgt Saville’s death.
The man he was trying to rescue from the railway lines - a 29-year-old - sustained electrocution injuries. He was also taken to hospital where he remained on Tuesday, with injuries which are not believed to be life-changing.
Robert Jenrick, MP for Newark, whose constituency includes Balderton, paid tribute to the “exceptional bravery” of Sergeant Graham Saville.
Writing on X, formally known as Twitter, Mr Jenrick said: “Sergeant Graham Saville selflessly gave his life to save someone else.
“All of us in Newark salute his exceptional bravery and self sacrifice, which won’t be forgotten.
“My thoughts are with his partner and children and all his colleagues at @nottspolice.”
Assistant Chief Constable Allan Gregory, of BTP, described Sgt Saville’s death as “truly devastating news”.
“On behalf of everyone at British Transport Police I’d like to offer sincere and heartfelt condolences to Sergeant Saville’s family, and to our colleagues at Nottinghamshire Police,” he said.
“Detectives from BTP are conducting a full and thorough investigation in order to establish the full circumstances of what happened last week.
“We remain in the very early stages of this investigation and we will be working alongside the Coroner’s Office as it progresses.
“It is one of the darkest days in policing to lose an officer in the line of duty, and Sergeant Saville’s loved ones will be at the forefront of our minds throughout our enquiries.”