Britain faces a “lockdown Christmas” amid fears of copycat jihadist attacks after the London Bridge atrocity.
Police plan extra armed patrols and could limit leave to put more officers on the steets.
Extra barriers and turnstile checks will be in place at football matches and other events.
Sniffer dogs will be used to detect guns and explosives and undercover counter-terror teams will watch for any unusual activity.
Authorities are reviewing past cases to spot fresh plots and have a record 700 inquiries under way.
London attacker Usman Khan, who killed two people last month, had slipped through the net.
Security expert Bruce Jones said: “We are facing copycat and retaliatory ‘lone-wolf’ attacks.”
* Austrian authorities have foiled a plot to bomb a Christmas market in Vienna and other locations. Three men are in custody.