Ramin Mehmanparast, an Iranian Foreign Ministry spokesman, told a London news conference Tuesday there was no evidence to support the claim and accused Canada of hostility toward Iran, The New York Times reported.
"The Islamic Republic of Iran is the biggest victim of terrorism, but the extremist administration of Canada has put 'Iranophobia' on its agenda [in] recent years," he said.
The comments come after two men, Chiheb Esseghaier and Raed Jaser, were arrested Monday for allegedly plotting to attack a train operated by Via Rail Canada, officials said.
Canadian police said Monday there was no indication Iran sponsored the plan but said the suspects received direction from al-Qaida elements in Iran.
Officials did not say how the link to al-Qaida had been made, the Times said.
Authorities declined to identify the suspects' nationalities or describe their immigration status.
Canada broke diplomatic relations with Iran in September as a result of several issues, including Iran's nuclear program, the Times reported.