Britain's top domestic intelligence chief says authorities are investigating dozens of terror plots and warns of future attacks, which she says could involve chemical or even nuclear devices.

Eliza Manningham-Buller

The head of Britain's domestic spy agency, MI5 rarely speaks out publicly, but Eliza Manningham-Buller told a select invited audience that the authorities are currently tracking some 30 active terror plots and 200 extremist cells involving some 16,00 individuals.

She said some of the plots have clear links to al Qaida in Pakistan.

Manningham-Buller also said that many of the suspects are British and she warned that young British Muslims are being recruited to extremist causes and ideologies at an alarming rate.

Prime Minister Tony Blair said Friday he fully agrees with the assessment of his spy chief.

Tony Blair

He said, "This is a threat that has grown up over a generation. I think she [Manningham-Buller] is absolutely right in saying it will last a generation."

Britons became painfully aware of the threat of home grown terrorism in July 2005 when four young local Islamic radicals blew themselves up in London's subway system and on a bus, killing 52 commuters and injuring hundreds more.

In August of this year, police said they had foiled a plot to blow up transatlantic airliners. Earlier this week a British Muslim convert, Dhiren Barot, was sentenced to life in prison for plotting to blow up major public sites and transport links in the United States and in London.

Mr. Blair says the terror threat persists.

"And, it can only be combated in the end, not just by proper measures on security. … but in addition to that, that we take on and combat the poisonous propaganda of those people that warp and pervert the minds, particularly of younger people," he said.

Mr. Blair has repeatedly rejected any link between Islamic terrorism and British foreign policy in the Middle East and Afghanistan. However, in her speech MI5 director Manningham-Buller said extremists are driven by what she termed, "a sense of grievance and injustice."

The intelligence chief said police had foiled five major plots since last year's bus and subway bombings. She said plots currently include the use of homemade improvised explosives, but she warned future threats would include chemical and even nuclear materials.