FARMERS across the region are being warned to expect more than a week of intense aircraft activity as the region plays host to a major international exercise.

Fighters and support aircraft from eight nations will be joining the RAF in a large scale, low-level operation designed to test their ability to work together.

In an effort to reduce noise and panic among livestock in remote areas, strict limits are being set on the levels at which flying will take place.

For the duration of the exercise, all visiting aircraft will be forbidden from flying below 500ft - double the usual 250ft low-flying limit for the RAF.

The National Farmers' Union has been briefed on the operation, and plans to monitor it through their members.

"Although we have been given assurances about the low flying there is always a possibility of livestock being disturbed," said David Collier at the NFU's York office.

"We were only told about this operation a week ago, which means we were not in a position to place an item in our regional journal, which is a pity."

The Country Land and Business Association (CLA) has also passed on warnings to its members - although it has asked them to understand the reasons behind the operation.

"The MoD had advised us of the exercise and it is only fair that we pass this on to our members, many of whom are still suffering badly from theeffects of the foot-and-mouth crisis," said the CLA's North-East regional director, Anthony Haslam.

Exercise Clean Hunter, which began yesterday, will continue until Friday, June 29.

In addition to the RAF it will involve Nato aircraft from the US, France, Germany, Norway, the Netherlands, Greece, Portugal and Belgium.

"It is designed to test Nato's ability to defend an area of responsibility," said an MoD spokesman yesterday.

"We can't work together in active situations unless we have tested it and tied it down.

"These sort of exercises have to be held. They are not always in this country, but this year it is us."

The electronic warfare range at RAF Spadeadam, in the Borders, will be targeted, and participating RAF stations will be used as simulated targets.