UK police
The warning arrived after the terror threat level in the UK was raised to "severe" Getty

Police officers have been told to be vigilant "for their own personal safety" following a rise in the terror threat from "substantial" to "severe".

The Association of Chief Police Officers (ACPO) offered advice to 130,000 officers across the UK as the threat towards police has "heightened".

Home Secretary Theresa May announced in August the terror threat level in the UK had risen to "severe", suggesting an attack is "highly likely".

May said the reason for the increase was due to "developments in Syria and Iraq where terrorist groups are planning attacks against the West".

The advice was also given following the arrests of four people in London on suspicion of being involved in the commission, preparation or instigation of terror acts.

Whitehall officials have said they believe the men may have been planning an "Isis-related" terrorist attack in the UK.

There have been no more specific threats and intelligence available, but ACPO are now reminding officers "of the need to be vigilant for their personal safety".

National Policing Lead for Counter-Terrorism, Assistant Commissioner Mark Rowley added: "The threat level to police officers and staff has been heightened, but we are used to confronting risk and danger, this is what we do on a daily basis, and we are well trained.

"We are informing our officers and staff of the heightened risk and reminding them to remain vigilant and alert to any possible dangers. We are asking them to follow existing policies and good practice. Measures are being put in place to increase the vigilance of officers and staff.

"All police forces constantly review their security and safety procedures and this will, of course, continue. You will see no major changes in the way we continue to police the UK and engage with our communities - our emphasis is on vigilance."

ACPO are also asking for the public's help in order to combat terrorism.

"We therefore continue to urge the public to remain vigilant and report any suspicious activity to police," a spokesperson added.

"In particular we need communities and families to bring to our attention anyone they perceive may be vulnerable or in danger of escalating towards terrorism."