NEW DELHI - Indian opposition leader Sonia Gandhi was questioned by money laundering investigators on Thursday, prompting her Congress Party to accuse Prime Minister Narendra Modi's government of running a "political vendetta".

The complaint against 75-year-old party president and her son Rahul Gandhi was lodged nine years ago by a member of parliament from Modi's Bharatiya Janata Party (BJP).

Rahul Gandhi, who is also a senior figure in Congress, was questioned several times last month in connection with the same case. They have both denied any wrongdoing.

"This is a conspiracy to silence us and the intention is to rid the country of any opposition parties," Congress spokesperson Pawan Khera told reporters on Thursday, before Gandhi left for questioning at the finance ministry's Enforcement Directorate.

A spokesman for the directorate, which investigates money laundering and violations of foreign exchange laws, was not available for comment.

Lawmakers from the Congress party staged a protest inside and outside parliament, holding posters and shouting slogans that accused Modi and his government of pursuing a political vendetta. The BJP lawmaker behind the complaint, Subramanian Swamy, accused the Gandhis of forming a shell company and illegally gaining control of property worth $300 million.

The assets had belonged to a firm that published the National Herald newspaper, founded in 1937 by India's first prime minister, Jawaharlal Nehru, who was Rahul Gandhi's great grandfather.

(Reporting by Shilpa Jamkhandikar; Editing by Simon Cameron-Moore)