David McKercher, chief prosecutor in the case, said in his opening statement
on Monday that the court would hear evidence showing Khawaja was part of
"a plan to build and detonate a 600-kilogramme ammonium nitrate-based fertiliser bomb that could cause massive destruction and loss of life".
Khawaja's lawyer, Lawrence Greenspon, has argued in pre-trial proceedings that more of the evidence gathered by the prosecution should be made available to his client to aid his case.
However, prosecutors say much of the evidence is from US and British intelligence agencies and therefore highly sensitive.
Security was tight around the courtroom on Monday, with security officers confiscating all gels and liquids and using a metal detector for those entering the building.
"Given the nature of the charges Mr Khawaja is facing, we thought it would be prudent to boost security," Joan McKenna, Ottawa's police inspector, told AFP news agency.
Khawaja is one of the first people to be charged under Canada's security legislation, passed after the September 11, 2001, attacks in the US.
Five other men were convicted in London last year and sentenced to life in
prison in relation to the case, while two other men were acquitted.
Khawaja's lawyers have said he would plead not guilty and have disputed any link between his case and the trial in the UK.
Legal experts see the case as a test of Canada's security legislation, which gives the government broader powers to keep intelligence information secret on national-security grounds and limits the ability of defendants to access evidence used against them.