LONDON, June 7: Pakistan is still being regarded here as the base for Al Qaeda from where terrorist activity in Britain has been planned and directed. But lately a significant number of British radicals are said to have travelled to Iraq to fight and some are believed to have returned with expertise in conducting urban terror attacks.

According to the Times, police are, therefore, monitoring lorries on key routes into London amid concerns that terrorists might copy tactics that have been used to deadly effect by insurgents in Iraq.

Security spot-checks are being carried out on petrol and chemical tankers, cement mixers and other vehicles that could be used by suicide bombers.

Bombers in Baghdad have blown themselves up in hijacked petrol tankers and, in at least three attacks this year, have used chlorine gas canisters in lorry bombs.

The checks follow a warning earlier this year by Sir Ian Blair, the Metropolitan Police Commissioner, that “vehicle-borne weaponry is the greatest danger that we can face”. But Scotland Yard stressed on Wednesday that it had no specific intelligence to suggest that a lorry-bomb attack was imminent.

The Metropolitan Police’s Counter Terrorism Command set up the checks as a precautionary measure but they have now been incorporated into ‘Operation Mermaid’, a long-running operation aimed at ensuring vehicle safety.

“A counter-terrorism element has been added to the routine work of checking vehicles carrying dangerous goods,” a police spokeswoman said.

“In addition to checking road-worthiness and the safety of the load, officers will also be looking to see if there is anything about a vehicle that makes them suspicious. There is constant monitoring of the methodology of terrorism overseas and we have seen vehicles like this used in attacks. It would be remiss of us not to take that into account.”