A prayer meeting was held at the Veer Bhumi, the memorial of Gandhi, where Sonia, Singh, Mukherjee and the late prime minister's children, Rahul and Priyanka, paid homage to him.
Leader of the Opposition in the Rajya Sabha Ghulam Nabi Azad and Ahmed Patel, political secretary to the Congress chief, were also present.
Rajiv was born on this day in 1944 and was assassinated on May 21, 1991.
In Amethi, which Rajiv represented in the Lok Sabha, people from different walks of life and Congress activists paid homage to the former prime minister.