Staff at RAF Menwith Hill are warning local residents not to be alarmedif they hear warning sirens from the base over the next couple of days.

The precautions follow in the wake of the world's worst terrorist attacks on America last week which left more than 5000 people dead.

Security drills and exercises will be practised by base staff over the coming weeks, together with an increase of patrols by Ministry of Defence and North Yorkshire police.

RAF Station Commander [RAF Liason Officer] Squadron Leader Humphrey Vincent said he hoped neighbouring communities would not be over-alarmed at the measures.

"The base, in keeping with other US-affiliated bases worldwide is operating a high-security posture", he said. We regret any traffic congestion some of our security measures may cause on the roads immediately adjacent to the base.