West Midlands Police has been issued with safety warnings following an alleged plot to kidnap and kill an on-duty officer.
A major security alert was triggered resulting in all officers being held on duty while they were briefed about the threat after the force received "anonymous information" regarding a potential attack.
The force said it had "implemented additional security measures" after receiving the information, which included giving officers a security reminder as well as advice on travelling to and from work in their uniforms.
The MI5 previously gave advice to police officers not to wear their full work uniforms while travelling to or from duty over fears they could be a target of a terrorist attack.
The Association of Chief Police Officers (ACPO) also warned officers to be vigilant "for their own personal safety" following a rise in the police's internal threat level from "moderate" to "substantial", meaning there is a strong possibility of attack.
Assistant chief constable Garry Forsyth said: "West Midlands Police treat all information relating to matters of security extremely seriously.
"In this particular case, we have received information relating to the safety of West Midlands Police officers and police staff. There is nothing at this time to suggest there is an increased risk to members of the public.
"We have taken the opportunity to remind all employees of the need to be vigilant. Our priority remains serving our communities and protecting them from harm. Officers remain on patrol and our staff continue to respond to calls for service as usual."
A West Midlands Police spokesperson added it does not believe there is an increased threat to the public following the alert.
The security alert arrived after Home Secretary Theresa May announced in August the terror threat level in the UK had risen to "severe", suggesting an attack is "highly likely".