Terming it as a "truly a special occasion," Gandhi hailed the founding father of South Africa's multi-racial democracy as a "courageous fighter" and a "symbol of indomitable spirit".
"Today when the world is confronted with a crisis of leadership with moral force, you stand out as a symbol of indomitable spirit. We pray and wish that the world continues to benefit from your wisdom and reassuring presence," she said.
Mandela, who is revered for leading the fight against white minority rule in the African country and then preaching reconciliation despite being imprisoned for 27 years, turned 95.
He served as the country's first black president from 1994 to 1999. He left power after five years as president.
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In her message, Gandhi also noted "we all have been concerned about your health in recent times. Our people join the people of South Africa and the rest of the world in conveying our sincere wishes for your speedy recovery."
Wishing him good health, peace and happiness, Gandhi said, "your life has been a message of struggle and sacrifice. Your humility, spirit of forgiveness and compassion has touched all those, who have the privilege of knowing you.