Canada’s prime minister, Justin Trudeau, has renewed his calls for answers from Iran following admissions that its military shot down the Ukraine Airlines flight 752 passenger jet.

“What Iran has admitted to, is very serious. Shooting down a civilian aircraft is horrific,” said Trudeau, speaking to reporters early Saturday afternoon from Ottawa. “Iran must take full responsibility.”

The comments from Trudeau mark the strongest demand yet from the prime minister, who has repeatedly called for a thorough and transparent investigation of the crash.

In a call with Iranian president Hassan Rouhani earlier on Saturday morning, he reiterated the importance of access to the crash site for Canadian officials so they can assist in the investigation – and compensation for the victims.

Canadian representatives have faced barriers from Iranian authorities in accessing the crash site. Only three of its 10 visa applications have been approved, with officials due to land in Tehran on Sunday. Members of its transportation safety board are also waiting for the right documentation before travelling.

But as Canada demands answers on the crash, the lack of diplomatic relations has further complicated an already difficult task.

The country cut diplomatic ties with Iran in 2012, a move that has since caused numerous logistical headaches for its sizeable diaspora population, including direct flights between the two countries and access to consular services. Since then it has relied on the assistance of Italian diplomats to represent its interests in Iran.

On Saturday, Trudeau said the plane crash had been a national tragedy. While the government has recently revised the number of citizens onboard from 63 down to 57, 138 passengers on the plane were bound for Canada. Many of those killed were students, leaving a number of schools and universities in mourning this week.

“I had to chance to sit with some of the families of the victims. They are hurt, angry and grieving,” said Trudeau. “They want answers. They want justice.”

Following admissions of culpability from senior members of the Iran government, some in the Iranian-Canadian community have reiterated calls for accountability.

“Those who have committed this crime of shooting down a passenger airplane and those who have been responsible in releasing false information must be held accountable,” the Iranian Canadian congress said in a statement following the news.

“The families of the victims of this horrible tragedy must be supported in any way deemed appropriate and desired by the families, including through restitution.”

Others, however, were more blunt in their assessment of Iran’s admission.

“I am burning from the inside,” an Iranian university student in Canada, who was friends with victim Mansour Asnaashary Esfahani, told the Guardian. “It’s all fury inside me.”

But he also said the news provided slight relief, over fears that students had jeopardised their safety by booking a “cheap flight” in order to save money.

“[Victims’] families were blaming themselves why they didn’t help their children travel with better airlines.”