GPS trackers will be blocked today by the military at popular hiking spots during Europe's biggest war game.

Services will go down intermittently at Faraid Head and Loch Ewe, and fishing vessels are also being warned, Nato Joint Tactical Exercise Planning Staff said.

A message will be broadcast by Stornoway and Shetland Coast Guard before and after the jamming period.

Nato JTEPS said: “Denial of GPS services through the jamming of the GPS signal is an essential part of preparation for military operations and the training is likely to impact on both military and civilian users on land, sea and in the air.

“The ability to conduct jamming is spread throughout the modern world. Consequently, military forces are required to train under such conditions in order to demonstrate the effects it has on systems and to train personnel in other modes of operating.

"Crews should be aware of these limitations and use alternative means of navigation during jamming periods to confirm their position and check the equipment on completion.

"All military vessels and aircraft will be ordered to maintain a lookout for any abnormal vessel behaviour during jamming periods and warn vessels as required."

Thousands of service personnel are taking part in what is described as the largest military exercises in Europe.

As well as live firing on the Cape Wrath weapons range in Sutherland, the GPS denial operations will be conducted during limited periods.

Joint Warrior is a multinational exercise that involves numerous warships, aircraft, marines and troops, and provides "a complex environment in which UK, Nato and allied units can go through training together in tactics and skills for use in a combined joint task force".

The exercise runs through a range of scenarios, including crisis and conflict situations, that could be realistically encountered in operations such as disputed territory, terrorist activity and piracy conflicts.

A spokesman for the Royal Navy said: "All relevant authorities, including aviation and maritime communities have been consulted and procedures are in place for unforeseen eventualities."

The first break will be between 7am and 7pm today – for periods no greater than 45 mins – and on Monday between 5pm-6pm, and Tuesday from 10am to 5.30pm.