The account ‘Canadian Ukrainian Volunteer’ had posted about war missions - posing in uniform and holding weapons - to some 118,000 followers for months.
In one post, a man with a blurred face held a cigarette in his mouth underneath the words: “Mike filled me in on the rats in the cellar. Their anguish sustains me. The more they squirm the harder I get.”
But Twitter users identified a string of holes in the alleged fighter’s posts, believing that the person was posing with a fake rifle, helmet and magazines, and even using photos of others.
The account has since been deleted.
In a series of Tweets one user, under the name Kung Fu Panda, accused the person behind Canadian Ukrainian Volunteer of posing with a fake shovel bought from Amazon, a fake Mk7 and replica AK-47 magazines.
Meanwhile Ukraine Weapons Tracker, an account which claims to debunk and track usage of material in Ukraine, said: “We passed by all the scandals before, but this is just getting ridiculous - the famous [Canadian Ukrainian Volunteer] account, who claims to be fighting on the side of Ukraine, is a liar”.
Aric Toler, director of training at the open-source investigations group Bellingcat, said that photos of his dented body armour had also been stolen from a Telegram account.
“The original photo was from Ukrainian police of someone illegally selling military equipment on Telegram,” he said, posting photos of the classified ad.
To prove the location of the alleged fighter - the final nail in the coffin - an open-source intelligence expert under the name NexusIntel sent a personal message.
The expert claimed on Twitter the user’s IP address was linked to Ontario, Canada, and not Ukraine.
“Why should we care?” NexusIntel wrote.
“He never asked for donations, which is great. So he didn’t do it for financial gain. But Ukrainians and foreigners are dying for Ukraines right to exist.”
Throughout the Russian invasion of Ukraine, there has been a slew of misinformation including falsely credited images and stories of supposed war victories.
A number of groups have formed to tackle the issue, including an all-female team behind media database, Dattalion.