The portraits, which feature the kids licking, riding and otherwise engaging with portable video game systems, are a stealthy series of “guerilla marketing” advertisements for Sony’s PlayStation Portable, or PSP. The pieces do not feature a Sony logo or other identifying marks and have caused graffiti artists to cry foul, charging that the giant corporation is co-opting the art form for a crass commercial purpose.

Or, as one artist succinctly scrawled over an advertisement: “FONY.”

“There is a war going on between people putting up the Sony graffiti and taggers,” Department of Public Works Director Mohammed Nuru said. Taggers, or graffiti artists, have taken to splashing the figures with red paint, scratching them out with markers and scrawling messages blasting Sony.

Nuru, who said the advertisements are illegal without city permits, said corporations are increasingly resorting to graffiti and street stencils to spread the word.

In recent years, The City has caught NBC, IBM and the makers of “Zorro” resorting to such advertisements, Nuru said. NBC and IBM both paid The City more than $100,000 to clean up street stencils for a Linux program and a science fiction miniseries that appeared on the USA Network, which is owned by NBC.

The Sony advertisements began appearing in early November in the Mission District, Haight-Ashbury and Civic Center as well as six other cities, including New York, Los Angeles, Chicago and Philadelphia. Smith said Sony paid local businesses to use the wall space and city graffiti artists to spraypaint the work.

“Our intention was to go out into the urban environment and creatively engage people,” Sony spokeswoman Molly Smith said. “We certainly never intended to be provocative.”

While some participants in vigorous online discussion devoted to the topic see the graffiti as a legitimate advertisement — especially since the property owners were paid — others see the ads as one more piece of graffiti in neighborhoods already plagued by tags. Nuru falls into the latter category and is instructing businesses to paint over the graffiti.

“It encourages young people to deface city property,” Nuru said.

Maureen Healy, principal of Healy Communications in San Francisco, said companies are increasingly turning to this type of “guerilla” advertising to reach young people, who may be jaded by traditional TV and print ads. She said the idea is to generate a buzz for the product by making it seem like hip people are into the product. The technique is often called “viral marketing.”