Sonia Gandhi in hospital after infection

Leader of India's main opposition Congress party Sonia Gandhi is in hospital for treatment of an infection.

Mrs Gandhi was admitted to Delhi's Ganga Ram Hospital on Friday evening, Press Trust of India news agency quoted party spokesman Ajay Maken as saying.

In 2011 Mrs Gandhi went to the US to receive surgery for an undisclosed medical condition.

Last year, she was taken to a Delhi hospital for a few hours after she fell ill during a debate in the parliament.

Mrs Gandhi was suffering from a respiratory tract infection and her condition is now stable, party officials said.

"She is currently under observation," a Congress spokesman told AFP news agency.

Mrs Gandhi, 68, is the widow of former prime minister Rajiv Gandhi.

She is the head of the Nehru-Gandhi dynasty, which has ruled India for most of the time since independence in 1947.

Her party lost the 2014 general elections to the Hindu nationalist Bharatiya Janata Party.