Some of the most popular online action and warfare games feature actual weapons and have links to the manufacturers of those weapons.
As Electronic Arts prepared to market Medal of Honor Warfighter, the latest version of its top-selling video game released in October, it created a Web site that promoted the manufacturers of the guns, knives and combat-style gear depicted in the game.
Among the video game giant's marketing partners on the Web site were the McMillan Group, the maker of a high-powered sniper's rifle, and Magpul, which sells high-capacity magazines and other accessories for assault-style weapons.
Links on the Medal of Honor site allowed visitors to click through on the Web sites of the game's partners and peruse their catalogs.
"It was almost like a virtual showroom for guns," said Ryan Smith, who contributes to the Gameological Society, an online gaming magazine. After Mr. Smith and other game enthusiasts criticized the site, Electronic Arts disabled the links, saying it had been unaware of them.
The video game industry was drawn into the U.S. debate about gun violence last week when the National Rifle Association accused producers of violent games and movies of helping to incite mass shootings like the one in which a gunman killed 20 children and 6 educators at a school in Newtown, Connecticut.
While studies have found no connection between video games and gun violence, the case of Medal of Honor Warfighter illustrates the way the firearms and video game industries have quietly forged a mutually beneficial marketing relationship.
Many of the same producers of firearms and related equipment are also financial backers of the N.R.A. McMillan, for example, is a corporate donor to the group, and Magpul recently joined forces with it in a product giveaway featured on Facebook. The gun group also lists Glock, Browning and Remington as corporate sponsors.
Makers of firearms and related gear have come to see video games as a way to promote their brands to millions of potential customers, marketing experts said. Magpul and Electronic Arts made a video posted on YouTube about their partnership.
"It is going to help brand perceptions," said Stacy Jones, the president of Hollywood Branded, a company that specializes in product placement in movies and television shows.
Assault-style rifles made by Bushmaster Firearms have a roster of credits that any actor would envy, including appearances in Call of Duty Modern Warfare 2, a part of the popular Activision series.
The gunman in the Connecticut killings, Adam Lanza, used a semiautomatic rifle made by Bushmaster, which is a unit of the Freedom Group.
The most recent entry in the Call of Duty franchise, Black Ops II, featured models of weapons that are also made by Barrett and Browning. Another popular game sold by Electronic Arts, Battlefield 3, depicts assault rifles and pistols similar to those made by Colt, Heckler & Koch, Glock and Beretta.
The U.S. military also uses Call of Duty and other video games for recruitment and to train soldiers.
An Activision spokeswoman said she had not been able to get a response because of the holiday season. Several other companies, including McMillan, Magpul, Browning and Barrett, did not respond to telephone calls or e-mails. The National Rifle Association also did not respond. A Glock spokesman could not be located for comment.
In a statement, Electronic Arts said video game makers, like film producers, "frequently license the images of people, sports franchises, buildings, cars and military equipment." The company added that it did not receive payments for using branded images in Medal of Honor.
A spokesman for the Freedom Group, Ted Novin, said in an e-mail that Bushmaster had "received no payment, nor have we paid for placement of our products in Call of Duty."
"The gaming and entertainment industry routinely use likeness of our products without our permission," he added in the e-mail. But he did not respond when asked whether Activision had received the Freedom Group's permission to depict its products in Call of Duty.
The Freedom Group is owned by the private equity firm Cerberus Capital. After the Connecticut school shooting, Cerberus announced that it would seek a buyer for the Freedom Group.
Many players of shooting games like Medal of Honor and Call of Duty say they enjoy the simulated violence and the chance to fire weapons virtually, even if they never touch real guns. But along with some game fans, some firearms enthusiasts have become uncomfortable with the growing ties between video games and gun companies.
A few years ago, when the marketer of a submachine gun, the Skorpion, publicized its depiction in some games, the editor of The Firearm Blog, which follows industry developments, expressed surprise.
"I think most companies want to distance themselves from violent video games," wrote the editor, Steve Johnson.
Over the past decade, handguns made by Glock have become such standard fare in movies and television shows that the Austrian manufacturer received a lifetime achievement award in 2010 from Brandchannel.com, a product marketing Web site.
Game publishers like Activision and Electronic Arts race against one another to create the most realistic games, said Laura Parker, associate editor for GameSpot Australia, a gaming Web site.
"They believe the use of real-world brands -- be it clothing, tactical equipment or guns -- is a way to ensure that games like Call of Duty and Medal of Honor feel as close to real life as possible," Ms. Parker said via e-mail.
Some video game makers use depictions of weapons that are slight modifications of real ones or alter their names, avoiding possible legal complications.
But most established video game developers and publishers, given the huge amount of money invested in a game, seek out explicit authorizations or licenses from product manufacturers, said Matthew Syrkin, a lawyer at Hughes, Hubbard & Reed in New York who represents companies in the video game industry.
"There is a material risk in putting anything into a game unless you have a license," said Mr. Syrkin, who added that such agreements also protected manufacturers from having their products depicted in an illegal or unflattering manner.
The Connecticut shooting is not the first time violent video games have been blamed for causing violence, including mass shootings. A similar outcry followed the 1999 shootings at Columbine High School in Colorado by two teenagers who played Doom, then a popular video game.
Last year, a Norwegian who killed 77 people said later that he had honed his shooting skills by playing many hours of Call of Duty.
In the case of the recent promotional Web site for partners of Medal of Honor Warfighter, a spokesman for Electronic Arts said it had taken action after discovering that game players could click through to its partners' sites.
"We felt it was inappropriate and took the links down," Jeff Brown, a spokesman for Electronic Arts, wrote in an e-mail.
But Mr. Smith, the game enthusiast who wrote about the links, said the company had not gone far enough. Mr. Smith said the direct link was gone, but visitors to the site could still search for a gun and "take a few extra steps to buy it."
"I personally think they should not have real weapons in the games in the first place," he said. "It's just bad to link things you can do in a game with tools of death you can use in real life."