He reportedly fell down the stairs at the hotel where he was staying after the concert in Nazrul Mancha auditorium, the NDTV said on Tuesday. Doctor at CMRI hospital said the singer was brought dead.
Many reports suggested the singer had a cardiac arrest or a heart attack, but Kolkata-based Bangla daily the Anandabazar Patrika reported a post-mortem examination will be conducted to confirm the cause of his death.
KK started his career in jingles and broke into playback with an AR Rahman soundtrack in 1996.
His 1999 debut album ‘Pal’ was critically acclaimed. From the early 2000s, he blazed a career in playback singing and recorded a wide range of popular songs for Bollywood films.
KK has recorded songs in Hindi, Tamil, Telugu, Kannada, Malayalam, Marathi and Bangla, among other languages.
Political leaders, actors and fans tweeted condolences. "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," Prime Minister Narendra Modi wrote.
"Extremely sad and shocked to know of the sad demise of KK. What a loss! Om Shanti," actor Akshay Kumar tweeted.
KK is known for many songs, to name a few, "Tu Hi Meri Shab Hai", "Awarapan Banjarapan", “Jab Tu Ne Keh Diya Alvida”, "Tadap Tadap Ke" and ““Hum Rahe Ya Naa Rahe Yaad Aayenge Ye Pal."
Fans in Bangladesh have also expressed shock on social media over his demise.