A court granted bail to opposition leaders Sonia Gandhi and her son Rahul today in a case involving the alleged misappropriation of party funds that has become a political flashpoint with the ruling party.

The mother-son duo made a rare appearance in a dingy Delhi courtroom to answer summons in the lawsuit brought by a member of Prime Minister Narendra Modi's party.

Senior Congress leader Kapil Sibal said the court granted bail to party chief Sonia and Vice-President Rahul without any conditions after a brief hearing.

Hundreds of members of the Congress party were massed outside the court premises in a show of support for the torchbearers of the Nehru-Gandhi dynasty that ruled India for more than four decades after independence in 1947.

Congress party leaders blamed Modi for unleashing a political vendetta against the mother-son duo, saying he was trying to snuff out those opposed to him since his election in 2014.

"We will fight this vendetta on every front. Make no mistake about it," said Kamal Nath, a senior leader, as he arrived in court along with other senior members of the party.

BJP leader Subramanian Swamy who has brought the lawsuit has pledged to send the Gandhis to jail, alleging they formed a shell company and illegally gained control of properties worth $300 million belonging to a newspaper founded by first prime minister Jawaharlal Nehru.

The family has denied any wrongdoing.