Indian film personalities such as Akshay Kumar, Karan Johar, Kumar Sanu, and Varun Grover paid tribute to singer KK, who died in Kolkata on Tuesday night. He was 53.

The velvet voice, who represented the many tones of the Indian youth growing up in the 1990s and 2000s, was known for his varied discography which included romantic ballads like Tadap Tadap, Bas Ek Pal, Aankhon Mein Teri, disco numbers Koi Kahe, It's The Time To Disco, and non-film tracks such as Pal and Aapki Dua.

The singer, whose real name was Krishnakumar Kunnath, performed at a concert organised by a college at Nazrul Mancha in south Kolkata for almost an hour in the evening.

He was "feeling heavy" after reaching his hotel, and soon collapsed, officials said.

He was taken to a nearby private hospital where doctors declared him brought dead around 10 pm, they said.

Doctors at the hospital said they suspected "cardiac arrest" to be the cause of the death.

As the news of his sudden death broke, condolences from contemporaries, associates from the film industry, and fans started pouring on social media.

Prime Minister Narendra Modi led the tribute to the popular singer.

The prime minister said he was saddened by the untimely demise of KK, whose songs, he said, reflected a wide range of emotions.

"Saddened by the untimely demise of noted singer Krishnakumar Kunnath popularly known as KK. His songs reflected a wide range of emotions as struck a chord with people of all age groups. We will always remember him through his songs. Condolences to his family and fans. Om Shanti," Modi said in a tweet.

Union Home Minister Amit Shah remembered KK as a "talented and versatile" singer.

"His untimely demise is very saddening and a huge loss to Indian music. With his gifted voice, he has left an indelible impression on the minds of countless music lovers. My deepest condolences to his family and fans," Shah wrote on Twitter.

A senior officer of the Kolkata Police told PTI that a post-mortem would be conducted on Wednesday to ascertain the exact reason for the death.

Bollywood superstar Akshay Kumar said he was "shocked" to know about the demise of the singer, who had recorded songs across languages such as Hindi, Tamil, Telugu, Kannada, and Bengali.

"What a loss! Om Shanti," he wrote on Twitter.

Regarded as one of the most versatile singers of his generation, KK was able to mould his voice to suit the on-screen persona of the country's biggest stars such as Shah Rukh Khan, Salman Khan, Emraan Hashmi and Ranbir Kapoor.

As an independent artist, his popular albums 'Pal' and 'Humsafar' stand the test of time and are a walk down memory lane for the millennials who are now all grown up today.

One of the early hits of KK was the song 'Yaaron Dosti' from the 1999 coming-of-age film "Rockford", which is one of the best odes to friendship in the modern era.

Veteran singer Kumar Sanu said he was unable to come to terms with KK's death.

"I cannot comprehend. He was one of my most favourite singers," Sanu told PTI.

Filmmaker Karan Johar said it was heartbreaking news.

"Heartbreaking news on the sudden passing away of such an incredible talent . RIP KK the entertainment world has lost a true artist today .Om Shanti," Johar wrote.

Lyricist-writer Varun Grover paid a heartfelt tribute to KK, an artist whose songs, he said, were all about loss and vulnerability.

"KK was an artist you'd discover in private. His best works were all about personal moments of loss & vulnerability," he said.

In an emotional post on Twitter, filmmaker Srijit Mukherji bid adieu to his "newest friend" with whom he bonded over the song recording sessions along with veteran lyricist Gulzar for his upcoming Hindi film "Sherdil".

"In a state of total shock.Just met him last month for the 1st time & felt that we'd known each other for years.The chatter wouldn't just stop.And I was so moved to see the love he had for Gulzar saab.He said he stepped into this world with Chhor aaye hum & sang it as a tribute," Mukherji wrote as he shared videos from their sessions.

KK started his film playback career with Gulzar when he sang the memorable track "Chhod Aaye Hum Woh Galiyaan" composed by Vishal Bhardwaj for the 1996 film "Maachis", also directed by Gulzar.

The singer-lyricist duo went on to collaborate for films such as 2001's "Aks", 2002's "Filhaal " and "Saathiya", and "Jhoom Barabar Jhoom" in 2007, among others.

"Farewell @KK_Pal, my newest friend. Will miss you. I wish we could have had more sessions on music and food and cinema," wrote Mukherji in a follow-up tweet.

"We had been friends for 27 hours. He was a versatile singer and a performer. Cannot imagine he could leave us in this way," music director Jeet Ganguly added.

Singer-songwriter Armaan Malik said he was "extremely sad and devastated".

In KK's death, the Indian music industry has lost another icon this year following the demise of Lata Mangeshkar, Bappi Lahiri, Punjabi singer-Congress leader Sidhu Moosewala, he said.

"These losses.. all of them feel so personal," he added.

Actor R Madhavan said he was heartbroken. KK had memorably sung the heartbreak song "Sach Keh Raha Hai Deewana", which was picturised on Madhavan in the film "Rehna Hai Tere Dil Mein".

"... lost a wonderful human and a great voice today. Rest In Peace bro. The heavens are luckier," he tweeted.

KK was on a two-day tour to Kolkata and was supposed to return to New Delhi on Wednesday.

The singer is survived by wife and two sons.