A native of Kozhikode district, Sasi, whose full name was Irruppam Veedu Sasidharan, was a diploma holder from Madras School of Arts.
Some of his well-known blockbusters include Alkoottathil Thaniye, Kanamarayathu, Aksharangal and Vadakaykkoru Hrudayam, Itha Ivide Vare, Angadi, Ee Nadu, Vartha, Devasuram and Avanazhi.
Sasi blurred the divide between the commerce and art in Malayalam films and was instrumental in moulding several superstars of the industry such as Mammootty, Mohanlal and veterans like late Jayan and Sukumaran.
Vellathooval, released in 2009, was Sasi's last movie, which he directed after a long gap. He also had some Tamil and Hindi movies to his credit.
Sasi, who was planning a comeback to the industry in recent times, was a winner of national and state awards.
In 2015, the Kerala government presented him with the J.C. Daniel Award, the highest film honour in the state, in recognition for his overall contribution to the film industry.
Chief Minister Pinarayi Vijayan condoled the demise of Sasi and said he was a filmmaker who rewrote the conventional formula in the Malayalam film industry.
Sasi's long-term friend and Tamil superstar Kamal Haasan tweeted: "My friend for 45 years I.V. Sasi is no more. The industry and I mourn a great technician. My support and love to my sister Seema Sasi and family."
Mourning his death, Mammootty said, "I feel sad on the demise of my beloved friend."
Calling him the "master of Malayalam movie industry", Mohanlal said, "Portraying the life of commoners, I.V. Sasi was a man who created wonders on the silver screen. I salute the master of Malayalam movie industry who made the viewers and actors, including me, understand the basics of cinema."
Mammootty's son Dulquer Salmaan wrote on Facebook, "RIP Sasi uncle! He created an Era of his own in Malayalam Cinema. Have fond memories of him from my childhood."
Sound designer Resul Pookutty tweeted, "The man who rewrote the course of mainstream Malayalam cinema I.V. Sasi is no more. We had been in discussions on a film together, it's my personal loss!"
"One of the greatest film makers of mainstream Indian cinema bids goodbye. We will miss you Sasi sir! So many personal memories!" Prithviraj Sukumaran posted.
Young actor Nivin Pauly tweeted: "RIP Sasi Sir. You will be truly missed."
