There were still serious concerns about his welfare as a prisoner of war, Senator Wong said as she called for his release.
"The Australian government has received confirmation from Russia that Oscar Jenkins is alive and in custody," she said in a statement on Wednesday.
"We have made clear to Russia in Canberra and in Moscow that Mr Jenkins is a prisoner of war and Russia is obligated to treat him in accordance with international humanitarian law, including humane treatment.
Foreign Minister Penny Wong said Russia is obligated to treat Oscar Jenkins humanely. (Mick Tsikas/AAP PHOTOS)
"If Russia does not provide Mr Jenkins the protections he is entitled to under international humanitarian law, our response will be unequivocal."
Senator Wong said she had also spoken with her Ukrainian counterpart the International Committee of the Red Cross president.
The Department of Foreign Affairs is providing consular assistance to Mr Jenkins' family.
Mr Jenkins was the first Australian combatant reportedly captured by Russian forces and his death would have marked the first for an Australian prisoner of war in more than 70 years.
Prime Minister Anthony Albanese said Russian authorities had told Australian officials Mr Jenkins was alive but he was reticent to offer official confirmation just prior to Senator Wong's statement.
"If that is the case it certainly would be welcome," he told ABC TV on Wednesday.
Anthony Albanese said Russian authorities had told Australian officials Oscar Jenkins was alive. (Richard Wainwright/AAP PHOTOS)
"It's something that we have demanded information on and we are demanding more information so that we can be certain that what has been suggested is, in fact, the case."
In a social media video circulated in December, Mr Jenkins was shown speaking a mix of broken Russian and English.
The Russian embassy in Canberra has been contacted for comment.
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