Workers in many high profile buildings in the UK have been evacuated following the terror attacks in the US.

The London Stock Exchange, the Lloyds Building, Canary Wharf and the NatWest Tower, in London, were cleared following the destruction of the World Trade Centre in New York and attacks on the Pentagon.

US and British firms in the City sent workers home as a precaution.

One worker at Canary Wharf, which houses Britain's tallest tower, said: "We were watching what was happening in America when suddenly the power cut out in our office and the fire alarm went off.

"I don't know why it did, but nobody needed much more encouragement to get out."

Scotland Yard said it had not ordered any evacuations, and that it was up to individual companies to decide if they wanted to send staff home.

"We are monitoring events which are unfolding in the United States and are vigorously exploring any consequences for London and the rest of the country," said a spokesman.

Canary Wharf was attacked by the IRA on 9 February 1996, killing two men and causing at least �85m of damage.