Gandhi led her party to victory in 2004 but nominated Manmohan Singh for the post of prime minister [EPA]

Sonia Gandhi, the head of India's ruling Congress Party, who underwent a surgery in the US for an undisclosed medical condition, has returned to the country.

Janardhan Dwivedi, the Congress spokesman, said Gandhi returned to New Delhi, India's capital, early on Thursday and was fine. He gave no other details.

Gandhi was operated upon in early August.

The party gave no details of her illness or the location of the hospital. News reports have said the operation took place in the US.

Last month, India's Tehelka news magazine said on the microblogging site Twitter that Gandhi was admitted to New York's Memorial Sloan-Kettering Cancer Centre.

She is the 64-year-old widow of Rajiv Gandhi, the slain former prime minister, and is widely viewed as the most powerful person in India.

She took over the Congress party in 1998 and declined the premiership despite leading the party to victory in 2004 elections.

Instead, she nominated Manmohan Singh as prime minister, with many analysts considering her to be more powerful than him, governing India behind the scenes from her bungalow in New Delhi.

Absence strongly felt

Gandhi's absence was strongly felt by her party during the 12-day anti-corruption agitation, which was mishandled by senior government officials.

She anointed a four member advisory committee, which included her son Rahul Gandhi and potential future prime minister, to oversee party affairs in her absence.

Apart from Rahul, the quartet comprised Dwivedi; Ahmed Patel, the Congress political secretary; and AK Antony, the federal defence minister. All of them are seen as close advisers to Gandhi.

Her leftist leanings have proved a strong influence over the Singh government, and she has pushed pro-poor policies such as food subsidies and guaranteed employment for villagers.

Source: Agencies