Three men were found guilty of terrorism offences on Monday, including a teenager believed by prosecutors to be the youngest Briton to be convicted of an offence under the Terrorism Act.

Hammaad Munshi, 18, Aabid Hussain Khan, 23, and Sultan Muhammad, 23, were found in possession of "huge volumes" of terrorism material, including al Qaeda documents and information on poisons and firearms, police said.

Detectives said the men were "facilitators" who provided exclusive, up to date information on terrorist techniques, training, weapons and explosives.

"These are not the actions of curious individuals, or even those who are sympathetic to terrorist objectives," said Detective Chief Superintendent John Parkinson, head of the Leeds Counter Terrorism Unit.

"They are the actions of people who pose a very real threat to our communities."

The Crown Prosecution Service (CPS) says the charges carry a maximum penalty of 10 years in jail.

Munshi had excellent IT skills, hosting his own website and using the Internet to circulate terrorism material including technical documents on how to make napalm and homemade explosives.

He was just 16 when he was arrested at his home in Dewsbury, West Yorkshire, when he returned from school.

A CPS spokeswoman said he was believed to be the youngest person to be convicted of a terrorism offence in Britain.

"He was certainly the youngest ever to be charged with a terrorist offence," the spokeswoman said.

Khan was the leading figure, detectives said.

He was very active in promoting al Qaeda ideology in Britain and using the Internet to recruit supporters, pointing people to secure chatrooms where they could be influenced to join training camps in Pakistan.

Police said Khan and Muhammad, both from Bradford, possessed some of the most significant propaganda videos released by al Qaeda, along with a step-by-step guide to making a suicide vest.

"While these men may not have been actively planning acts of terrorism themselves, they sought to incite others for terrorist purposes, promoting al Qaeda ideology and training programmes."

The men, who will be sentenced at a later date, were found guilty at London's Blackfriars Crown Court of possessing or making articles connected to terrorism.