Story highlights Prosecutors say the three suspects were inspired by a decree from ISIS spokesman

All have pleaded not guilty to terrorism charges

Prosecutors say the men were planning an attack with knives and had bought a hunting knife online

London (CNN) Three men are on trial in London, accused of planning to carry out a terrorist attack involving knives.

Haseeb Hamayoon, 28, and cousins Nadir Ali Syed, 22, and Yousaf Shah Syed, 20, have all pleaded not guilty.

Prosecutors say the three were inspired by a fatwa, or decree, issued by ISIS spokesman Abu Mohammed al-Adnani, a document described as "truly chilling" by Max Hill, the lawyer for the UK's Crown Prosecution Service.

Hill told jurors the 11-page fatwa was aimed at Muslims throughout the world and encouraged acts of terrorism and murder, justifying the killing of police and servicemen.

He said the fatwa instructed followers to "Rig the road with explosives for them. Attack their bases. Raid their homes. Cut off their heads. ... Hunt them wherever they may be. ... Remove their families from their homes and thereafter blow up their homes."

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