Family members of the 17 Canadian residents arrested on terrorism charges outside a heavily guarded courthouse in Brampton, Ontario, a suburb of Toronto. (Reuters)

Toronto, June 4 (Reuters): Seventeen Canadian residents, including some with Indian names, arrested on terrorism charges had amassed enough explosives to build huge bombs and were planning to blow up targets in densely populated Ontario, police have said.

The group possessed three tonnes of ammonium nitrate ' or three times the amount used in the 1995 federal building bombing in Oklahoma City that killed 168 ' and were preparing to make bombs, Mike McDonell, of the Royal Canadian Mounted Police, said.

The police arrested 12 men and five young people, who are said to be inspired by al Qaida. The adults were from Toronto and a suburb, Mississauga, and from Kingston, Ontario.

The police showed off a haul they described as bomb-making equipment, a cell phone in a box with wiring, a board apparently used for target practice, a computer hard drive and army fatigues.

“This group posed a real and serious threat,” McDonell said. “It had the capacity and intent to carry out attacks. ... The modus operandi is similar to other attacks that have taken place around the world.”

The FBI said some of the suspects may have had limited contact with the two persons, one with roots in Bangladesh, recently arrested in the US on terror charges.