The exercise will begin near Edinburgh and will continue at smaller sites and individual properties across Scotland and the North East of England until October 5.
Therefore, members of the public may notice increased emergency services activity in certain areas around Edinburgh, the Lothians, the East of Scotland and Northumbria.
The exercise will allow the emergency services, Governments and other agencies to practice and plan for terrorist incidents.
The exercise, which is not taking place in response to any specific threat, is the result of over a year of preparation and is part of a series of ongoing exercises.
No members of the general public will be involved and the exercise areas will be cordoned off and tightly controlled to minimise disruption.
It is inevitable that some noise may travel outside of the cordoned areas. This should not cause alarm and Police Scotland and Northumbria Police will be taking steps to inform people in local residential and business communities what to expect.
The exercise will not affect day-to-day policing or emergency service responses, which will continue as normal throughout the exercise.
The public should continue to report any concerns they have or if they see any suspicious activity by dialling 101 or 999 in an emergency. Anonymous reports can be made to the anti-terrorist hotline on 0800 789 321.
Assistant Chief Constable Bernard Higgins from Police Scotland said:
“Police Scotland and other police forces throughout Britain regularly assess and exercise their Counter Terrorism resources and capabilities to ensure we can respond appropriately to any incidents, which may arise.
“Exercise Border Reiver is the culmination of months of planning with partner agencies from across the UK and the scenario that will unfold over the three days is a realistic, challenging and complex set of circumstances that could arise during a terrorist incident.
“In addition to uniformed officers, a range of specialist Police Scotland resources will be in play for the exercise and this will result in some significant activity within the public domain. Please rest assured this all forms part of the live-play scenario and there is no risk to the public.
“The public should be reassured that we are constantly testing and exercising our plans along with our partners. Police Scotland is committed to ensuring that Scotland is capable of responding to the terror threat that faces the UK.”
Assistant Chief Constable Darren Best, of Northumbria Police, said:
“This exercise has been organised to test the response of the emergency services and other partner agencies to a cross-border incident. It is in no way linked to a specific or increased threat in our region.
“We regularly carry out exercises to test contingency plans and the co-ordination of the response to a major incident to ensure we are prepared to keep our communities safe.
“We want to reassure people the exercise will not affect day to day policing and emergency service response which will continue as usual throughout the exercise.”