Koo Hara was found dead at her home in Seoul on Sunday.
Goo Hara was a member of the South Korean idol group Kara. The cause of death was still under investigation.
K-pop singer Goo Hara passed away over the weekend.
South Korea's Yonhap news agency quoted local police in the Gangnam district police station in Seoul, saying that the singer had been found dead at 6 p.m. local time in Seoul.
In June, a month after she was found unconscious at her home and hospitalised, she said on social media that it was hard to fight depression and vowed to respond sternly to malicious online comment.
Her last post on Instagram, shared with her 1.5m followers on Saturday, was a photograph of herself in bed with the caption: "Good night".
The news of her death comes about six months after an alleged suicide attempt in May. The 28-year-old apologised for causing "concerns and a commotion" over the incident.
Goo had completed a mini-tour in Japan and released a Japanese-language single, "Midnight Queen", earlier this month.
Kara was one of the few Korean pop music groups that witnessed huge popularity overseas, particularly in Japan, at a time when many other K-pop groups were aspiring for a breakthrough on the global stage.
The world is mourning the death of Goo Hara. It is reported that her ex-boyfriend, hairdresser Choi Jong-bum, threatened to release a sex tape and "end her entertainment career". She was best friends with fellow K-pop star Sulli, according to the New York Times.
Her former partner was given a suspended jail term in August for physically assaulting and blackmailing the star.
Kara, her former band, were one of the first K-Pop groups to a breakthrough on the worldwide stage.