The 25-year-old was found after her manager went to her home in Seongnam because had not answered phone calls for hours, an official from Seongnam Sujeong Police Department said on Tuesday.

Kim Seong-tae said there were no signs of foul play and police did not find a suicide note.

"The investigation is ongoing and we won't make presumptions about the cause of death," Kim said, adding that security camera footage at Sulli's home showed no signs of an intrusion.

In a statement sent to reporters, SM Entertainment, Sulli's agency, said her death was "very hard to believe and sorrowful".

Sulli's legal name was Choi Jin-ri.

She began her singing career in 2009 as a member of the girl band f(x) and also acted in numerous television dramas and movies.

She was known for her feminist voice and outspokenness that was rare among female entertainers in deeply conservative South Korea.

She recently appeared in a TV show and spoke out against the online backlash she received over her lifestyle.

Australian Associated Press