A police officer has been killed while attending a reported burglary.
PC Andrew Harper, of Thames Valley Police, died at about 23:30 BST on Thursday in Berkshire.
Police have arrested 10 people aged between 13 and 30 on suspicion of murder and are in custody at stations across the area.
A cordon has been put in place at the scene near the A4 Bath Road between Reading and Newbury at the crossroads near to Sulhamstead.
Prime Minister Boris Johnson said he was "deeply shocked and appalled" by PC Harper's death.
Mr Johnson said: "My thoughts are with Pc Harper's family, friends and colleagues at this terrible time."
Andy Fiddler, from Thames Valley Police Federation, said: "This is totally devastating news.
"All our thoughts - and the thoughts of the entire police family across the UK - are with the family, friends and close colleagues of PC Andrew Harper who died last night."