Ten people have been arrested on suspicion of murder after a police officer was killed while attending a reported burglary in Berkshire, west of London.
Prime Minister Boris Johnson said he was "deeply shocked" and "appalled" at the news PC Andrew Harper had died after a "serious incident" at around 11.30pm last night near the A4, Bath Road, between Reading and Newbury.
Thames Valley Police said ten boys and men aged between 13 and 30 have been arrested on suspicion of murder and remain in custody at various police stations in the force area.
The incident occurred at the crossroads of Ufton Lane and Lambdens Hill, near to the village of Sulhamstead, police said.
UK Labour leader Jeremy Corbyn told the PA news agency he was "totally shocked" by the death and said it highlighted the need for more police officers on the streets.
Police said they were still establishing the circumstances in which PC Harper, from the Roads Policing Proactive Unit based at Abingdon Police Station, was killed while carrying out his duties.
Officers remain at the scene of the incident, which is cordoned off while evidence is gathered.
Yesterday afternoon forensic investigators could be seen gathering items that lay on the road and taking photographs. Two white tents have also been erected.
Police were also seen searching the inside of a grey BMW that was at the scene, according to witnesses. Pictures of the scene show a blood trail on the road leading across the junction.
Ufton Lane and Lambdens Hill remain closed but the A4, Bath Road, has reopened, police said.
The incident comes after a police constable was run over by a suspected car thief in Birmingham last week.
The married 42-year-old traffic officer from West Midlands Police is facing "potentially life-changing" injuries, a senior officer told PA.
This came just days after Metropolitan Police constable Stuart Outten, 28, was left with head and hand injuries after challenging a motor offences suspect allegedly armed with a machete in Leyton, east London.
Andy Fiddler, from Thames Valley Police Federation, said the death of PC Harper was "totally devastating", adding: "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."
Deputy Chief Constable Jason Hogg 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."
16/08/19— Thames Valley Police (@ThamesVP) August 16, 2019
Statement from Thames Valley Police Chief Constable John Campbell following the tragic death of PC Andrew Harper. pic.twitter.com/EjU2Dkjhx0
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 10 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 our investigation, no matter how insignificant it may seem, please leave details on our website or call 101."