The world's biggest gaming platform for children, Roblox, has removed two games that allowed players to fight and kill each other as Russians or Ukrainians.
One of them, called War on Larkiv: Ukraine, was showcased to users in the Roblox discovery section.
It clocked up 90,000 plays in less than two weeks.
Roblox said that both games violated its community standards and removed them within four hours of being contacted by the BBC.
War on Larkiv was based in a fictional city that resembled the real city of Kharkiv, where hundreds of people have died in indiscriminate shelling after Russia's invasion of Ukraine in February this year.
The other game, called Battle for Ukraine, had been on the Roblox website for months.
It allowed players to watch the bombing of cities such as Mariupol, which was besieged and largely destroyed by Russian forces earlier this year.
Fifty million players, mainly children, log in to Roblox every day to explore, play mini-games and create their own "experiences".
There are millions of these player-generated experiences.
The most popular are showcased to Roblox players through a curated home screen, but others can be found using the search function.
War on Larkiv: Ukraine grew in popularity because it was showcased and had a review score of 71% from users.
It had also gained an audience on TikTok, with 4.7 million views of videos related to the title.
The game encouraged players to upgrade their weapons in exchange for Roblox's in-game currency, Robux.
The game page read: "Grab your guns and choose your side to fight in the War on Larkiv: Ukraine. Heavy combat is taking place right now in the fictional city of Larkiv, soldiers strive with hope and destiny."
Players could choose to fight for Ukraine or Russia, with a kill count on each side updating throughout the live game that anyone on the platform could take part in.
The BBC monitored the game on and off for two days and found it had a continuous player base of about 10 to 40 people, with many sharing game chat in English, Ukrainian and Russian.
A Roblox spokesman said: "We have strict Community Standards which govern the portrayal of real-world events. Both of the experiences in question have been removed for violating our standards following an assessment by our moderation team."
Ukrainian game developer Grisha Bolshakov, who fled his home in Kharkiv and is now living in the UK, said he would never try to make an entertainment game about the war.
"Obviously a game with this sensational topic will resonate and generate interest on social platforms, but I would never touch this topic for an entertainment product,
"It's not helping to educate players morally or take a real look at rather sad things. It's just making fun from the meat grinder happening in the real world."
Controversies are not new to Roblox, a huge sprawling world of games valued at about $24bn (£18bn).
There are also other war simulation games seemingly based on active Middle Eastern conflicts that have been available for over a year.
"The model is broken," technology and ethics researcher Stephanie Hare says of Roblox's moderation system.
"There is an argument that the company has the right to profit from content that some people find offensive, but clearly these games broke their own decency rules, so why wasn't it spotted before a reporter found it?
"It comes down to incentive - there's no penalty or enforcement, so the company can just rely on inadequate tools and staffing and this will keep happening."
Unlike many games companies, Roblox has not stopped or suspended trading in Russia since the invasion.
At a recent Roblox developer conference, Chief Executive Dave Baszucki said Russia sees more than two million active Roblox users a day, according to Bloomberg reporting.