Derbyshire police have paid their respects to an officer who was killed while on duty last night.
PC Andrew Harper, of Thames Valley Police, died at 11.30pm in Berkshire while he was attending a reported burglary.
Ten men, aged between 13 and 30, have been arrested on suspicion of murder and are currently in police custody.
The incident happened near to the A4, Bath Road, between Reading and Newbury.
Derbyshire police today tweeted: "Awful news from @ThamesVP about a police officer being murdered while doing his job. Sending our thoughts to his family, colleagues, and friends. The thin blue line got thinner today. #RIP #PCAndrewHarper."
Flags at Derbyshire police HQ are being flown at half mast as a mark of respect.
Deputy Chief Constable Jason Hogg, of Thames Valley Police, said: “Our deepest thoughts at this time are of course with Andrew’s friends and family, who are being supported by specially trained family liaison officers.
“Our thoughts also extend to all of Andrew’s colleagues within Thames Valley Police.
“As a force we are devastated at the loss of our colleague and will all be supporting each other at this difficult time.”
Senior investigating officer, Detective Chief Inspector Stuart Blaik, of the Thames Valley Police Major Crime Unit, said: “This is a tragic incident, and I would like to reassure the public as well as our officers and staff that we have launched a full and thorough investigation to establish what has happened.
“We have made a total of ten arrests in connection with this incident, and those arrested are currently in police custody. Those arrested are all male and aged between 13 and 30.
“I would appeal to anyone who witnessed this incident to get in touch."
If you have any information which you think could be at all relevant to the investigation, no matter how insignificant it may seem, visit www.thamesvalley.police.uk/tua/tell-us-about/cor/tell-us-about-existing-case-report/ or call 101.