People using social media have been mounting patrols in Luton following of a mother of four on her doorstep.
Saima Khan was killed at her home in Overstone Road on Monday night. There have so far been no arrests for the murder.
The groups have been warning each other if they believe they have seen anything suspicious.
But police have advised they have increased patrols in the area.
A police spokesman said: “There have been increased patrols in Luton following the murder of Saima Khan and these will continue over the weekend. We want to reassure residents this tragic incident is being thoroughly investigated by a large number of specialist officers and we would remind them not to speculate around the circumstances.
“We have a dedicated team that looks at any emerging series in the county and remind residents to report any suspicious activity or criminal behaviour to the police rather than taking matters into their own hands.
“Anyone with information is asked to call police on 101. Always call 999 in an emergency.”