Swaraj passed away at AIIMS, Delhi after suffering a cardiac arrest. She was 67.
"Delhi govt will observe two days state mourning as a mark of respect in the memory of former Chief Minister & senior leader respected Sushma Swaraj ji," Deputy Chief Minister Manish Sisodia tweeted.
Chief Minister and AAP national convenor Arvind Kejriwal condoled her death, saying the country has lost a great leader.
"India has lost a great leader. Sushma ji was a very warm and remarkable person. May her soul rest in peace," Kejriwal tweeted.