Much of the command, control and inspiration for terrorist attacks in the United Kingdom during the last five years has been derived from al-Qaeda's remaining core leadership in the tribal areas of Pakistan, head of Britain's intelligence service said on Monday.

Addressing the Society of Editors' annual conference in Manchester, MI5 chief Jonathan Evans said, "often the planning used young British citizens to carry out the attacks."

The theme of the conference was "A Matter of Trust".

Evans cautioned that there were high levels of "covert activity by foreign intelligence organisations in our country."

He said that in spite of the "Cold War ending nearly two decades ago, my Service is still expending resources to defend the UK against unreconstructed attempts by Russia [Images], China and others, to spy on us. "

"A number of countries continue to devote considerable time and energy trying to steal our sensitive technology on civilian and military projects, and trying to obtain political and economic intelligence at our expense," said Evans.

"As I speak, terrorists are methodically and intentionally targeting young people and children in the UK. They are radicalising, indoctrinating and grooming young, vulnerable people to carry out acts of terrorism," he said.