Jonghyun, full name Kim Jong-hyun, was one of the five members of Shinee, who have had a string of number one hits in their home country.
The Korean Herald said he was 28 years old. He was taken to hospital after being found unconscious in an apartment in Seoul, according to reports.
Police told the BBC Korean Service that suicide will be investigated as a possibility.
South Korean news agency Yonhap reported that emergency services were alerted by the singer's sister, and that he was later pronounced dead at hospital.
Jonghyun shot to fame when the band was formed by K-Pop hit factory SM Entertainment in 2008.
As well as being a singer and an accomplished dancer, he played a large part in the group's songwriting and production, and launched a successful solo career in 2015.
He has also made headlines for voicing his opinion on issues like the government's education policy and for speaking out in support of LGBT rights.

Tributes have been paid on Twitter.

source:https://royalsgist.com/2017/12/18/korean-top-idol-star-jonghyun-committed-suicide-monday-police-reports/

Rip

R.I.P....

A lonely soul in a crowded world.