Police force in Britain warns staff to take extra security measures after anonymous tip

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A British police force has told staff to be vigilant after it received an anonymous threat or warning.

West Midlands Police says staff have been told to take "additional security measures."

British media reported that the threat concerned a plot to kidnap and kill a police officer.

The force says patrols are continuing normally Tuesday. Assistant Chief Constable Garry Forsyth said the force had "received information relating to the safety of West Midlands Police officers and police staff" and was reminding all employees to be vigilant.

Security forces are on heightened alert amid fears a "lone wolf" an attack.

In May 2013, two self-styled "soldiers of Allah" stabbed an off-duty soldier to death in London. In October, five men were charged with plotting to kill police or soldiers in London.