Authorities arrest two members of the Toronto 18 group as they unload what they believe are large quantities of ammonium nitrate. (CBC)

Video evidence released Tuesday includes footage of a massive simulated explosion, a taste of the kind of havoc that members of the so-called Toronto 18 bomb plot sought to inflict on Canada's largest city.

That video is among a number of clips collected by authorities in their case against one of the alleged kingpins in the plot.

Zakaria Amara was one of the ringleaders in the plot to recruit and train extremists to carry out attacks on two Toronto buildings and at an unnamed Ontario military base, which never transpired.

Amara pleaded guilty Oct. 8 to knowingly participating in a terrorist group and intending to cause an explosion for the benefit of a terrorist group — and is the fourth adult to admit guilt in the affair.

On Tuesday, Justice Bruce Durno, who has presided over the case, agreed to release the tapes in response to requests made by the CBC and the Globe and Mail. Neither the prosecution nor the defence had any objections to the footage being released.

RCMP footage shows a controlled explosion of a fertilizer bomb modelled on specifications detailed by Zakaria Amara. (CBC)

Among the most striking images included in the footage is the controlled detonation conducted by the RCMP, which was based on a recipe concocted by Amara for a one-tonne fertilizer bomb.

The flaming explosion creates a huge inverted mushroom cloud of thick black smoke and easily flips over a nearby steel shipping container.

Authorities have said that such a blast in downtown Toronto would have caused catastrophic damage, and would have killed or at least seriously injured people.

Khalid, Gaya caught red-handed

Another clip — filmed by Amara himself — captures the 24-year-old successfully testing a sophisticated cellphone-activated bomb trigger in his apartment. The resulting sparks burn a hole in his carpet.

The videos also show a SWAT team intercepting Saad Khalid and Saad Gaya — who have already pleaded guilty in the plot — who are unloading what they believe is three tonnes of ammonium nitrate fertilizer from a truck.

Another man, Ali Dirie, has also pleaded guilty to charges under the Terrorism Act.

Zakaria Amara, 24, pleaded guilty on Oct. 8 to participating in a terrorist group and intending to cause an explosion for the benefit of a terrorist group. (Reuters)

Last year, Durno also found Nishanthan Yogakrishnan, 21, guilty of participating in, and contributing to, a terrorist group.

Seventeen at the time of the offences, he was tried as a youth but received an adult sentence of 2½ years before being released in May in consideration of time served before trial.

In all, 17 men and youths were arrested in the Toronto area in June 2006 and detained following an investigation by the Canadian Security Intelligence Service. An 18th person was arrested in August 2006.

Seven of the 18 people arrested subsequently had their charges dropped or stayed.