A police officer is in hospital after being seriously injured in a "shocking" attack in Doncaster.
South Yorkshire Police said they were called to reports of a vehicle crash on Cleveland Street at about 07:30 BST.
The officer, 45, was assaulted when three people fled the area, running towards Cherry Tree Road.
The force said his injuries are not believed to be life-threatening. Two men and a woman have been arrested on suspicion of robbery and assault.
A spokesperson said: "Officers attended [after receiving reports of the crash] and pursued the individuals on foot to an address near Cherry Tree Road, where an incident occurred in the garden of a property.
"At this time, a male police officer, 45, from Doncaster, suffered serious head injuries and was taken to hospital in a critical condition.
"His condition is now described as stable and the injuries are not currently thought to be life-threatening."
Ch Supt Tim Innes added: "This was a shocking incident and highlights the dangers police officers face on a daily basis, not just in South Yorkshire but across the UK."
The force has appealed for any witnesses to come forward.