The victim, a man in his 40s, was airlifted to hospital on Tuesday evening, with his condition described as serious following the attack in the town of Gillingham, southeast of London.

Prime Minister Keir Starmer said he was "shocked and appalled" by the incident. "All our thoughts are with the soldier and our Armed Forces community, who serve to keep us all safe," he added.

"I wish him a swift recovery."

Kent Police said a 24-year-old local man was arrested on suspicion of attempted murder within half an hour of officers being called to the scene, near the British Army's Brompton Barracks.

"Enquiries to establish the circumstances are ongoing," the force said in a brief statement.

The attack has echoes of the 2013 murder of British soldier Lee Rigby, who was hacked to death by two Islamist extremists on a southeast London street.

Earlier on Tuesday, Anjem Choudary, the radical preacher whose proscribed Islamist group inspired that pair, was found guilty by a UK jury of directing a terrorist organisation.

Officials are yet to indicate any motive in the latest attack.

UK media said the victim was wearing his military uniform at the time of the attack, but police and the army have declined to confirm the reports.

A British Army spokesman said: "We're very sorry to confirm that a soldier has sustained serious injuries in an attack.

"We will continue to work closely with Kent Police to understand what happened and support the investigation."

A witness who rushed to aid the victim told The Sun tabloid that the attacker had been on a moped before running at the soldier and stabbing him repeatedly.

The victim had "wounds all over his body", according to the witness.

"Blood was everywhere as I tried to apply pressure to his wounds until the police arrived," the witness added.

"When the guy's (soldier's) wife came out and started trying to pull the guy off he didn't even try to hurt her."

Defence Secretary John Healey called the attack "shocking" and said his thoughts were with the soldier and his family.