An attack on London during the 2012 Olympic Games poses a major security threat to Britain, the government said Monday in its latest assessment of risks from terrorism.
Ministers also acknowledged growing concerns over an attack using chemical, biological, radiological or nuclear weapons, and warned that al Qaeda affiliates in east Africa and Saudi Arabia are gaining strength.
Publishing an annual report on Britain's counterterrorism strategy, Britain's Home Office acknowledged that the 2012 summer Olympics pose an acute security challenge.
"The government is working on the assumption that the greatest threat to the games is international terrorism and that the threat in 2012 will be high," the document stated.
Officials fear terrorists could attempt raids similar to those in Mumbai, India, in 2008, arriving on small high-speed boats and using gangs of gunmen to attack targets in central London.
Britain announced Monday the opening of a dedicated maritime security center - focused in part on piracy in eastern Africa, but also aimed at bolstering the country's defenses against an attack from the water ahead of 2012. Security officials have expressed worries that an attack against London could be launched from the River Thames.
"Things like the attack on Mumbai and the forthcoming Olympics in 2012 made us realize we needed to look at the maritime domain more closely," Britain's terrorism minister, Alan West, said.
In a written statement to lawmakers, Home Secretary Alan Johnson said al Qaeda's core leadership in Pakistan and Afghanistan had been stymied over the last 12 months by military action in southern Afghanistan and strikes against key individuals. Since January 2008, seven senior al Qaeda leaders have been killed, he said.
But Johnson warned that groups in Yemen, Somalia, Saudi Arabia and Algeria are increasingly capable of mounting attacks overseas. He cited as proof the attempted Christmas Day bombing of an airliner at it approached Detroit.
"An increase in the capability of some al Qaeda affiliates and associated groups, highlighted by the attempted Detroit airline attack, demonstrates the evolving and diffuse threat we continue to face," Johnson said.
Authorities say Umar Farouk Abdulmutallab, the man charged with trying to blow up the plane, had links to known radicals in Yemen.
In the report, Britain's government said the threat of terrorists gaining access to chemical, biological, radiological or nuclear weapons had increased because of a surge in the trafficking of radiological material, and the sometimes inadequate security around decommissioned military material.
It disclosed that the U.K. routinely screens people and vehicles passing through British border crossings for signs of radiation.