Foreign Minister Marc Garneau's comments were among the strongest Ottawa has made about the January 2020 disaster.

"The behaviour of the Iranian government has been frankly unconscionable in this past 15 months and we are going to continue to pursue them so we have accountability," Garneau told a committee of legislators examining what occurred.

Iran's Revolutionary Guards shot down the Ukraine International Airlines flight shortly after it took off from Tehran Airport.

Iran said its forces had been on high alert during a regional confrontation with the United States.

Iran was on edge about possible attacks after it fired missiles at Iraqi bases housing US forces in retaliation for the killing days before of its most powerful military commander, Qassem Soleimani, in a US missile strike at Baghdad airport.

Garneau complained it had taken months of pressure for Iran, with which Canada does not have diplomatic relations, to hand over the flight recorders for independent analysis and said Tehran had still not explained why the airspace had not been closed at the time.

In March, Iran's civil aviation body blamed the crash on a misaligned radar and an error by an air defence operator. Iran has indicted 10 officials.

At the time, Ukraine and Canada criticised the report as insufficient. But Garneau went further on Thursday, saying it was "totally unacceptable ... they are laying the blame on some low-level people who operated a missile battery and not providing the accountability within the chain of command".

Canada would release its own forensic report on the disaster in the coming weeks, he said.

Australian Associated Press