TORONTO -- Islam is a "powerful weapon" that can wreak havoc on the world and Canada's military action in Muslim lands justifies the butchering of civilians, two accused terrorist plotters are heard saying in recordings played at their trial on Thursday.

Raed Jaser and Chiheb Esseghaier face multiple terror-related charges in an alleged plot to derail a train travelling from New York to Toronto. Not-guilty pleas have been entered for both men.

An undercover FBI officer, who posed as a wealthy American businessman with radical views, has testified that he befriended the pair and secretly recorded numerous conversations between them. Those recordings form crucial evidence in the case.

"Islam is a monster, is a beast," Jaser is heard saying on one intercepted conversation. "Islam is a very powerful weapon, OK, and if it's in the right hands...then you can bulldoze the whole world."

Jaser and Esseghaier were arrested in April 2013.

In September 2012, the undercover officer travelled to Toronto with Esseghaier, a Tunisian national doing doctoral research in Quebec, and was introduced to Jaser, a permanent resident of Palestinian descent.

On a late-night walk, Jaser and Esseghaier revealed the full extent of their alleged train plot to the officer, as well as a "long-term" plan to use a sniper to attack leaders in Canadian society, the trial has heard. The following day all three men met at a park as children played nearby, court heard.

As they sat under a gazebo sipping tea and grazing on Timbits, Jaser talked of his desire to have Shariah or Islamic law imposed in Canada to stop the "wickedness" that exists in Western society.

"Islam is here to conquer," he is heard saying. "There is no live and let live in Islam."

Despite his strong views, Jaser also repeatedly emphasized how important it was for the trio to "stay invisible" and "blend, blend, blend" into North American society.

"We are in a war," he is heard saying. "The war is deception ok, so you need to play certain parts."

Two short video clips of the men while they were in the park were played in court and showed Jaser dressed in a long white robe and a red chequered Islamic scarf on his head. Esseghaier is seen wearing a camouflage jacket and an orange baseball cap.

When talk switches to the specifics of the alleged train plot, the trio discuss Esseghaier taking a reconnaissance trip on a train during which he would examine the first-class carriage, court heard.

"When the loss is at the upper class...they will go crazy," Jaser is heard saying. "It will hurt them a lot."

Later, as Esseghaier and the undercover agent drive back to Montreal, court heard the officer ask how they could justify the deaths of innocent women and children who would be killed in the train plot.

Esseghaier is heard explaining that the carnage that would result from their terror plan was justified because Muslims were allowed to commit "haram" or forbidden acts to save their religion.

He is also heard saying that Canadian and American military action in Muslim lands has led to attacks on civilians in those countries, and that the "mujahedeen" need help getting rid of foreign soldiers.

"They are killing our women and our children in our country, so why we don't kill the women and their children in their country....God almighty, he told us in the Qu'ran to do to them as they are doing unto you," Esseghaier says. "The necessity of saving religion is higher than the necessity of saving life."

"It was chilling," the officer testified about Esseghaier's answer.

The trial has heard the alleged plot would see two men drill a hole in a railway bridge under cover of darkness to derail the train. The men would wait for a "green light" from radical contacts Esseghaier had overseas before the attack, court heard.

"If we do it under their green light, it will be more effective," Esseghaier is heard saying.

"We can show to the enemy that...our brothers overseas, they are able to start an attack at the time that they want."