There are grave fears for a former Canberra high school student after claims he was killed in Iran, amid representations by the Australian government to Tehran over the potential execution of prisoners.

Posts on social media accounts linked to the boy suggest he died on Friday, after reportedly being detained in Iran. The claims could not be verified.

However, wellbeing support has been offered to former classmates of the boy – who was not an Australian citizen – by his former high school in the ACT, Guardian Australia has confirmed.

Community members have also raised concerns with the government that another person – an international student studying at an Australian university – had been sentenced to death in Iran, although details of the case could not be verified.

The Australian government declined to comment on either case.

However, the federal government has made representations to Tehran about executions, including in recent days.

Thousands of protesters are estimated to have been killed during demonstrations in Iran in recent weeks.

A spokesperson for the Department of Foreign Affairs and Trade said Australia opposed the death penalty “in all circumstances for all people” and has pressed the Iranian government to cease its use.

“We have called on the Iranian government to cease killings, the use of force, and arbitrary detention in response to its violent suppression of recent protests,” the spokesperson said.

An ACT government spokesperson said the deputy chief minister and education minister, Yvette Berry, raised the matter with the office of Australia’s foreign minister, Penny Wong, on behalf of the school community.

“We understand representations were made to Iran on the matter,” the spokesperson said.

The ACT government spokesperson said additional wellbeing supports had been made available onsite for students at the school, which the boy attended until last year.

Families and staff had also been informed about free community support they could access, the spokesperson said. The ACT’s education department was also ensuring students at other affected public schools had access to such support.

Last August, the Albanese government expelled Tehran’s ambassador to Canberra after the nation’s domestic spy agency accused Iran of directing at least two attacks against Australia’s Jewish community.

Australia’s embassy in Iran also suspended operations, meaning there were no staff on the ground.

In December, demonstrations initially sparked by concerns over Iran’s economic crisis spiralled into anti-regime protests across the country.

Estimates of the death toll from the regime’s brutal crackdown on protesters vary substantially, with some suggesting it might be more than 30,000.

The official death toll released by the Martyr’s Foundation is 3,117, including members of the security services.

Calls have been growing inside Iran for an independent inquiry into the number of people killed after the government said it would oversee the publication of the names of the deceased.