POLICE will launch an campaign appealing for public help in the fight against terrorism.

Advertisements appearing in newspapers and on radio will encourage people to "trust their insticts" and report suspicious behaviour confidentially via a special phone line or through the Metropolitan Police website.

The campaign has not been launched in response to a specific threat, but police warn the possibilty of terrrorist attack remains real.

Peter Clarke, Specialist Operations Assistant Commissioner, said: "Just one phone call could contain a piece of vital information which could help disrupt terrorist planning and save lives.

"Terrorists will not succeed if suspicious activity is reported to the police. As people go about their normal day-to-day lives they may spot something which strikes them as suspicious.

"We're asking all members of the public - people who live in London, as well as those who work in and visit the city - to trust their instincts and contact the Anti-Terrorist Hotline on 0800 789 321 with any information they have. No piece of information is considered too small.

"We want people to look out for the unusual - some activity or behaviour which strikes them as not quite right and out of place in their normal day to day lives.

"Terrorists live within our communities, making their plans whilst doing everything they can to blend in, and trying not to raise suspicions about their activities.

"They have a lot of work to do before they attack. They need money and may commit cheque, credit card and identity fraud to finance their activities.

"Terrorists use chemicals. Do you know someone buying large or unusual quantities of chemicals for no obvious reason? Handling chemicals is dangerous, and maybe you've seen goggles or masks dumped somewhere?

"Observation and surveillance help terrorists plan attacks. Have you seen anyone taking pictures of security arrangements such as CCTV? Has it made you suspicious?

"Meetings, training and planning for terrorist attacks can take place anywhere. Do you know someone who travels but is vague about where they're going?

"Terrorists use computers - do you know someone who visits terrorist-related websites?

"I completely understand and appreciate that some people may have concerns or reservations about contacting the police - possibly they think their friends or family may find out, or they are worried that their suspicions may prove to have innocent explanations.

"Any information passed to the Anti-Terrorist Hotline is treated in the strictest of confidence. I make my assurances that information received is thoroughly analysed and researched before, and if, any police action is taken."

The Anti-Terrorist Hotline number is: 0800 789 321.

Information can also be passed on via the Met website at www.met.police.uk, by clicking on the red and white 'If you suspect it report it' icon.

The campaign will also run in the Greater Manchester, West Yorkshire and the West Midlands.