Sushma Swaraj died of cardiac arrest in Delhi's All India Institute of Medical Sciences.

The Rashtriya Swayamsevak Sangh (RSS) on Wednesday expressed grief over the death of BJP veteran Sushma Swaraj.

"The news of her sudden death is unimaginable, unbelievable, sad and painful," the RSS said in a condolence letter.

"She was happy with the recent historic development in the nation, as she expressed before she left us. We express condolences to her family in this moment of grief," the letter stated, referring the BJP-led government's decisions related to scrapping Aricle 370 in Jammu and Kashmir.

"About 45 years of her social, political life is ideal and worth following from many perspectives," the message signed by Mohan Bhagwat and Suresh (Bhaiyaji) Joshi stated.

Ms Swaraj had thanked PM Narendra Modi in her last tweet.

"Narendra Modi ji - Thank you Prime Minister. Thank you very much. I was waiting to see this day in my lifetime," she said in her last tweet on Tuesday, referring to the abrogation of Article 370.

She died of a cardiac arrest in Delhi's All India Institute of Medical Sciences (AIIMS) on Tuesday evening.

The BJP veteran was cremated with state honours this afternoon in the presence of top leaders including Prime Minister Narendra Modi, Home Minister Amit Shah and BJP patriarch LK Advani among others.

The former external affairs minister was cremated with full state honours on Monday evening.

Political leaders across the board had paid their tributes on the demise of the veteran politician.