SEOUL (AFP) - They don't fit the normal fan profile, but South Korea's 40-something K-pop aunties are every bit as obsessed with their idols as their teenage counterparts.

Posters and photos of one of K-pop's best-known boybands, BigBang, adorn every wall of Ms Lee Un Young's apartment in Seoul - a live-in shrine to a decade-long devotion.

The fact that she is old enough to be the mother of any one of the band's five members doesn't bother the 46-year-old housewife at all.

"There are a lot of auntie fans in their 40s like me, who started following BigBang when they were in their 30s," said Ms Lee, who has a particular soft spot for the group's leader, G-Dragon, who has carved out a successful solo career on the side.

She admitted to "feeling shy" when she first started going to BigBang concerts and other events when she was already a good 20 years older than most of the teenage girls around her.

"But then I slowly found some other fans who were around my age and we immediately clicked with each other," she said.

"These days, five of us get together once a month and all of our conversations revolve around BigBang and G-Dragon."

Ms Lee's husband, Mr Park Tae Kyun, is supportive and says he admires his wife's commitment, although he could do without the posters that cover even the windows of their apartment.

"Even in summer, we don't get any sunlight," he complained.

The K-pop phenomenon has its roots in the 1992 debut of Seo Taiji and Boys, a trio of hip-hop singers. The group's fusion of Western pop music and Korean lyrics struck an immediate chord with a generation that was coming of age in a newly affluent, newly democratic South Korea.

They were followed by the first wave of idol groups - like H.O.T - who spawned devoted and intensely competitive fan bases and became models for the boy and girl bands who would take the K-pop trend global over the next decade.

The idol group formula has evolved but its core image remains the same - young, attractive bands, with a carefully honed fashion sense and meticulously choreographed dance moves.

The obsessive nature of their fan bases can be extreme, especially the so-called sasaeng or stalker fans - mostly 13- to 17-year-old girls who have been known to break into their idols' homes.

Although the overwhelming majority of K-pop followers are either in their teens or early 20s, Ms Baek Sung Hee, a housewife in her mid-40s, sees nothing odd in her passion for the music.

"To me, age is just a number, nothing more," she said.

"And anyway, I know some K-pop fans in their 50s and 60s, so I'm a younger sister compared to them," she added.

Ms Baek and her friend, Ms Park Si Woo, 45, are both huge fans of the group Super Junior-M and one of its members in particular.

Henry Lau isn't even Korean, but he speaks it fluently and Ms Baek and Ms Park think the 25-year-old Chinese-Canadian singer is inspirational.

Ms Park was going through a personal crisis when she first heard Lau sing the title track from his 2013 debut mini-album Trap.

"I was very drawn to the song, it just made me want to become free and leave everything behind," she said.

So drawn, in fact, that she opened a snack bar in Seoul called Cafe Henry, which sells Henry burgers with various fillings.

Like Ms Baek, Ms Park said she knew a number of committed K-pop fans in their 60s who feel awkward about their musical passion.

"Some of them have told me they're just too embarrassed to admit they are fans," she said.

Younger fans actually seem quite accepting of the aunties - known as imo - and treat them with more admiration than scorn.

Ms Na So Young, a 22-year-old student, says the older women even turn out for airport events, when hardcore fans throng departure gates to see their favourite band leave on tour.

"Sometimes we miss breakfast because we head out to the airport in the early morning," she said. "Auntie fans bring lunch boxes and hand them out to everybody. It's like a family."

A less wholesome image is attached to the aunties' male counterparts - uncle or samchon fans - middle-aged men devoted to following K-pop's sometimes highly sexualised girl bands.