The beloved lead singer of Korea's most popular K-Pop boyband has died today at the age of 27.

Kim Jong-Hyun, who sang and performed as part of the chart-topping band SHINee, committed suicide, according to reports in the Korean media.

He was found inside a rented apartment in Cheongdam-dong, in the south of the capital Seoul. He'd checked into the serviced residence for two nights, Korean news channel YTN reports.

Police responded to a call from Jonghyun's sister, who was concerned that he was going to attempt suicide.

A statement from Gangnam Police confirmed that the talented musician's sister called officers with concerns that Kim was threatening to take his own life.

"On December 18, 2017 at 4:42PM Jonghyun's older sister reported to Police that her brother was about to commit suicide," said the statement.

(Image: Instagram)

"We went to his residence in Chungdam and discovered that he had attempted to commit suicide."

The statement added: "Emergency responders were with us at the time so we rushed him to the Konkuk University Hospital in a state of cardiac arrest."

His cause of death is said to be carbon monoxide poisoning, which could have been caused by breathing in fumes. It was thought he died en route to the hospital.

It's being reported by Korean news sites that Jonghyun left a suicide note, which his sister may have read.

In 2013, Jonghyun came under fire from trolls belonging to an ultra-conservative group.

He had changed his Twitter profile to represent his support for the LGBTQA community, which didn't go down well with ILBE Storage - a right-wing website based in Korea whose colloquial name is short for Ilgan Best, or 'popular daily'.

According to Dramafever.com, Jonghyun came "under attack" from members of the site, who joined SHINee's fan club website and reportedly posted some obscene pictures of women's bodies along with captions designed to humiliate.

In retaliation, the band's fans "declared war" on ILBE.

In what Dramafever.com reports was a supportive gesture to a transgender bisexual university student, Jonghyun had changed his Twitter profile image to one of the student's handwritten signs reading, "I am not OK", which had been hung up around the grounds of Korea University.

The singer also messaged the student to lend his support.

The messages, which were written in Korean and translated, read: "I am sending these messages for fear of the damage or attention caused to you by my tweet that you may not want. I support you.

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"As an entertainer, as a minority in a different definition who deals with the public, I feel a great sense of loss in this world where we don’t admit differences. Of course, this can’t be comparable to your feeling," Jonghyun told the fan.

(Image: Instagram/jonghyun.948)

"I support you shouting squarely that difference isn’t wrong. I don’t think you are a person who needs other’s consolation or concern. You are as strong as much. I wish you stay healthy, and have a warm end of the year."

Tributes from heartbroken fans have already flooded social media.

"Jonghyun's beautiful voice. Such a strong vocalist and such a good songwriter," tweeted one.

"He wrote one of my most favourite K-pop songs, Breathe. He had so much more to give. I'm so sorry he was in so much pain to do this. RIP Kim Jong Hyun."

Another wrote: "I really don't know what to think but i do know that my heart is broken. rest in peace kim jong-hyun."

And a third said in tribute: "Sending my condolence to Shawol and SHINee members and Jong Hyun's Family, of course. Kim Jong Hyun, rest in peace, you're talented. You're worth and the best. Once again, rest in peace."

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