"I was grieved to learn about the demise of your beloved wife Dr Shanthi Kumar today following a sudden illness," Jayalalithaa said in a condolence letter to Kumar, copies of which were circulated to the media.
"Although no words of solace would really be adequate in such circumstances, I wish to share your grief by conveying my deepest condolences to you and to all the other members of your family," she said.
"I pray that the almighty may give you the strength and fortitude to withstand this personal sorrow. May her soul rest in peace."