http://news.bbc.co.uk/1/hi/scotland/4258439.stm

BBC Scotland has been told that the Belgian authorities have been approached to supply up to four cannon for the Perthshire event.

Tayside Police said "no firm decisions have been made".

Firing jets of water at angry crowds is not unusual at G8 summits overseas. However, there is no tradition of using them in Scotland.

Vehicle mounted cannon have been deployed in Northern Ireland, but it is thought that it would be their first use in Scotland.

Tayside officers planning for the Gleneagles summit have been studying public order tactics across Europe.

The force has confirmed "all contingencies" are being considered.

Police sources said an approach has been made to Belgium to secure up to four cannon.

Tayside's chief constable, John Vine, insists no order has been placed.

But he said the use of "extreme measures" will be considered if intelligence suggests a need.

Deploying water cannon in Scotland would have to be approved by the country's most senior officers.