Sheila Dikshit displays the thumbs-up symbol as she rides a metro train in New Delhi. File / Rajesh Kumar Singh / AP

• She had been undergoing treatment for a heart ailment
• Dikshit served as chief minister of the capital for three consecutive terms, from 1998 to 2013
• Dikshit was blessed with a warm and affable personality, tweets Modi

Veteran Indian politician Sheila Dikshit, New Delhi's longest-serving chief minister, died on Saturday after a prolonged illness.

She was 81.

Dikshit died at a hospital in New Delhi, where she had been admitted for treatment for a heart ailment, New Delhi Television channel said.

A veteran leader of the opposition Congress party, Dikshit served as chief minister of the capital for three consecutive terms, from 1998 to 2013.

In a tweet on Saturday, the Congress party called her a "lifelong congresswoman" who "transformed the face of Delhi." Dikshit was elected as a member of India's Parliament in 1984, representing a parliamentary seat from the northern state of Uttar Pradesh. She also served as a federal minister from 1986 to 1989.

Prime Minister Narendra Modi wrote on Twitter that Dikshit was "blessed with a warm and affable personality" and "made a noteworthy contribution to Delhi's development." The country's president, Ram Nath Kovind, tweeted that her "term in office was a period of momentous transformation for the capital for which she will be remembered."

Dikshit had been undergoing treatment for multiple heart problems and underwent heart surgery in France last year.

She was defeated in India's general election in May by Modi's ruling Bharatiya Janta Party (BJP).

Associated Press