London: Britain was on high alert for suicide bomb attacks on May 14 after serial blasts by al-Qaida network against Westerners in Riyadh on May 13 left 29 dead and scores including nine Indians injured.

Fears of fresh outrages by Osama bin Laden's outfit intensified when wife of British Prime Minister Tony Blair, Cherie Blair pulled out of a London charity event on May 13 night after being warned that she had been singled out for a terrorist attack at a top hotel.

The Federal Bureau of Investigation (FBI) has warned UK that terrorists are plotting to hijack petrol tankers and turn them into horrific mobile bombs.

Scotland Yard has been warned by FBI that Osama's al-Qaida plans to launch the attacks in the UK.

One anti-terrorist detective said, "The belief is that something will happen soon."

"It's not a question of if we'll have suicide bombings in this country, but when," said leading terrorist expert Prof Paul Wilkinson.

Police across the UK have been ordered to report "any suspicious activity sightings" to a special hotline set up by Scotland Yard.

Freight companies carrying dangerous cargoes have been told to tighten security and check drivers.

A Scotland Yard spokesman said, "What the police are looking out for is anything unusual, like two fuel tankers being brought together in a place where they would not normally be seen."

PTI