Herald has revealed Australian Oscar Jenkins, who was taken captive by Russian forces in the Donbas region of Ukraine last month, was tortured “for days” before he was killed.

Soldiers who served alongside Oscar Jenkins in the Ukrainian armed forces say they are convinced their Australian comrade was killed by Russia's military shortly after being captured last year.

Russian Ambassador to Australia Alexey Pavlovsky has refused to confirm or deny whether Australian fighter Oscar Jenkins has been killed by the Russian military, as he faces renewed calls to confirm the status of the Melbourne-based fighter now feared dead.

Oscar Jenkins, an Australian teacher fighting for Ukraine, was reportedly captured and interrogated by Russian soldiers. His status and whereabouts are unknown.

Australia's Prime Minister Anthony Albanese responded on Wednesday to the alleged death of Oscar Jenkins, a Melbourne man captured while fighting for Ukraine, swearing to take 'the strongest action

The government is considering diplomatic retaliation if reports that Melbourne man Oscar Jenkins has been killed in Ukraine by Russian forces are confirmed.

Australia summoned the Russian ambassador over reports a Melbourne man had been killed after being captured by Russia while fighting for Ukraine, Prime Minister Anthony Albanese said on Wednesday.

Australia said Wednesday that "all options are open" in its response to the reported killing of one of its citizens after his capture by Russian forces in Ukraine.

Australia has pledged to take the "strongest action possible" if Russia is found to have deliberately harmed one of its citizens who was fighting alongside Ukrainian forces. Oscar Jenkins was captured last month by Russian troops,