Five extremists with links to hate preacher Anjem Choudary were jailed after being infiltrated by an undercover police officer, a media report said.
One of the men spoke of "40 trucks driving down Oxford Street full of explosives", Sky News quoted the Old Bailey as saying on Friday.
Each was jailed for between two-and-a-half years and six years for drumming up support for the Islamic State (IS) terrorist group.
They were arrested after an officer infiltrated the Luton chapter of the banned group Al-Muhajiroun (ALM).
During the operation, the police officer recorded hate-filled speeches over 20 months, delivered to up to 80 people, including young children.
They urged people to support the terror group and travel to Syria to fight.
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Group leader Mohammed Istiak Alamgir, 37, who hailed the Tunisia terror attack as a "victory", was handed six years of jail term.
Rajib Khan, 38, was dubbed as an "important and influential" member of the group and was jailed for five years.
He hailed the Charlie Hebdo atrocity in Paris as "excellent news".
Yousaf Bashir, 36, gave a speech for which he was given four years and six months in prison.
--IANS
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