Veteran Indian politician Muthuvel Karunanidhi has died at the age of 94.
He was being treated for age-related illnesses in Chennai (formerly Madras) in southern India's Tamil Nadu state.
Mr Karunanidhi served as the chief minister of Tamil Nadu five times between 1969 and 2011, and also played a key role in federal politics. He contested - and won - 13 elections in the state.
A school dropout, he made his name as a successful scriptwriter in Tamil films.
Police have increased security in Chennai amid fears of unrest among his supporters, who have gathered in the streets in large numbers.
Mr Karunanidhi died at 18:10 local time (12:40 GMT) on Tuesday, the Kauvery Hospital in Chennai said.
He was active in politics until his death and most recently contested the 2016 state assembly against his long-time opponent and bitter rival Jayaram Jayalalitha, who died later that year.
An atheist and self-declared rationalist, Mr Karunanidhi rose to political prominence in the 1940s as part of the Dravidian movement - which challenged the supremacy of upper caste Brahmins - and through his participation in anti-Hindi language agitations.
A prolific writer and a fiery speaker known for his wit and oratory, he enjoyed god-like status among his supporters.
Prime Minister Narendra Modi has led tributes to the veteran leader.
Deeply saddened by the passing away of Kalaignar Karunanidhi. He was one of the senior most leaders of India.— Narendra Modi (@narendramodi) August 7, 2018
We have lost a deep-rooted mass leader, prolific thinker, accomplished writer and a stalwart whose life was devoted to the welfare of the poor and the marginalised. pic.twitter.com/jOZ3BOIZMj
The hashtag #RIPKalaignar is also gaining traction on Twitter. Kalaignar means artist in Tamil, and the reference is a nod to his widely recognised contributions to film and literature.
"His popularity was rooted in his longevity. He's been a witness to everything that's happened in the state in the past six or seven decades," newspaper columnist Bhaskaran Krishnamurthy earlier told the BBC.
"He transformed Tamil literature, he's written stories, plays and poems, he's a reformist, he's the only leader of his stature."
Who was Muthuvel Karunanidhi?
- Born on 3 June 1924 in a village in Thiruvarur district
- A school dropout, he made a name as a screenwriter in Tamil films
- A founding member of the DMK when the party was formed in 1949
- Contested Tamil Nadu state assembly elections for the first time in 1957
- Contested 13 assembly elections in total and won a seat in all of them
- Was Tamil Nadu chief minister five times
- Besides film scripts, wrote stories, plays and poems
- Popularly called Kalaingar, the Tamil word for artist, for his contribution to cinema and literature