The number of terror suspects being monitored by Britain's domestic security agency, MI5, has risen by 25 percent in the last six months, BBC online reported Wednesday.
The approximately 2,000 people now being watched are thought to be actively involved in supporting al Qaeda, the broadcaster reported, and experts highlighted links which some have to terrorist training camps in Pakistan.
"I think this is the strongest connection that we are confronted with at the moment, not least because of the historical connections between Pakistan and Britain," Peter Neumann, from King's College London's defence studies centre, told the broadcaster. "This is most likely to be the greatest source of vulnerability -- at least for Britain."
In March, finance minister Gordon Brown announced that Britain's security services -- MI5 plus its foreign security counterpart MI6 and the Government Communications Headquarters (GCHQ) "listening post" -- would receive an extra 86.4 million pounds (127.2 million euros, 169.3 million dollars) this year.
This means that Britain's total annual security budget is now 2.25 billion pounds, more than double the figure before the September 11, 2001 terrorist attacks in the United States.
Last November, Dame Eliza Manningham-Buller, the then head of MI5 who retired last month, said that the agency was tracking 1,600 suspects from 200 groups, most with ties to al Qaeda. Nearly 30 terror plots were under investigation, she added.