Some of the 14 men arrested in London at the weekend — including a group detained while dining in a Chinese restaurant — could become the first to be charged with offences of encouraging terrorism and giving or receiving terrorist training.

Police were last night given extra time to question the suspects, and an extensive search was continuing in the 54-acre grounds of Jameah Islamiyah school near Crowborough, East Sussex, where the suspects regularly attended weekend camps.

Counter-terrorist sources told The Times that those detained included suspected ringleaders and young men who were being groomed as potential recruits to the jihad.

The group had been under surveillance by intelligence agencies for several months.

It used the school grounds, which include a lake and an area of woodland, for survivalist exercises. Young recruits had to listen to extremist lectures on religion and politics.

Police are believed to have intervened after intelligence reports indicated a discernible change in the nature of the rhetoric and language of the alleged recruiters.

Detectives believe that while the group was still being radicalised, no targets had been identified and any possible terrorist attack was a long way off.

One source said: “This is not a case of disrupting an imminent attack. What we are looking at is training and recruitment and encouraging others to take part.

“This operation was aimed at the process of radicalisation, at using the new powers we have to tackle glorification of terror and indoctrination of young people.”

The Metropolitan Police were granted warrants to further detain three of the suspects until Wednesday. Scotland Yard said the remaining 11 suspects can be questioned until Friday.

Since the July 7 bombings in London last year, senior Scotland Yard officers have been studying the process by which young British Muslims can be radicalised. They have identified several factors, including religious indoctrination, propaganda, outdoor “bonding” activities and the influence of preachers.

Police and the Crown Prosecution Service have been criticised in the past for not acting against “preachers of hate” such as Abu Hamza al-Masri, the jailed former imam of Finsbury Park Mosque — who in February this year was convicted of inciting murder — and Omar Bakri Mohammed, who went into exile in Lebanon.

But the powers to act against extremist speakers and terrorist recruiters were significantly strengthened by the Terrorism Act 2006, which received Royal Assent in March.

Counter-terrorist agencies believe that they now have the power to thwart the radicalisation process before there is any threat to public safety.

Scotland Yard said that the arrests in London were not connected to the ongoing inquiry into July 7 or to the arrests last month of 24 people in connection with the alleged plot to blow up transatlantic airliners.

Most of those held in the latest raids are believed to be British-born men of Pakistani origin, although one is reported to be a young black man who recently converted to Islam.

No arrests have been made at the Islamic school.

In a separate operation, police in Manchester arrested two men under anti-terrorist legislation and searched a number of properties in the Cheetham Hill area.

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