Describing former prime minster Manmohan Singh's death as a "personal loss", Congress Parliamentary Party (CPP) chief Sonia Gandhi on Friday said he was her friend, philosopher and guide and that in his death, the party has lost a leader who was the epitome of wisdom, nobility and humility.

In her message on Singh's demise, Sonia Gandhi said he leaves a void in the national life that can never be filled.

"We in the Congress party and the people of India will forever be proud and grateful that we had a leader like Dr Manmohan Singh whose contributions to India's progress and development are immeasurable," she said.

"In Dr Manmohan Singh's passing, we have lost a leader who was the epitome of wisdom, nobility and humility, who served our country with all his heart and mind. A luminous and beloved guiding light for the Congress party, his compassion and vision transformed and empowered the lives of millions of Indians," the former Congress president said.

Singh was loved by the people of India for his pure heart and fine mind, Gandhi said, adding that his advice, "wise counsel" and views were eagerly sought and deeply valued across the political spectrum in the country.

"Respected and admired by leaders and scholars all over the world, he was hailed as a statesman of immense wisdom and stature. Dr Manmohan Singh brought brilliance and distinction to every high office that he held. And he brought pride and honour to India," she said.

"For me, Dr Manmohan Singh's death is a deeply personal loss. He was my friend, philosopher and guide. He was so gentle in his manner but so resolute in his deeply held convictions.

"His commitment to social justice, secularism and democratic values was deep and unwavering. To spend any time with him was to come away enlightened by his knowledge and sagacity, moved by his honesty and integrity, and awed by his genuine humility," Sonia Gandhi said.

Earlier in the day, the CPP chairperson paid homage to Singh at his residence where his mortal remains are kept for people to pay their last respects.

She also attended a Congress Working Committee (CWC) meeting convened to pay tributes to the former prime minister.