The Enforcement Directorate (ED) on Tuesday questioned Congress President Sonia Gandhi for the second time in six days in the National Herald newspaper-linked money laundering case, officials said.

As ED officials quizzed Gandhi, 75, for six hours and asked her to appear before the agency for the third round of questioning on Wednesday, Congress workers staged 'satyagraha' in several parts of the country to protest against the alleged misuse of central agencies.

Congress leader Rahul Gandhi and several party MPs were detained by police at Vijay Chowk in the national capital. "India is a police state, Modi is a king," said Rahul, who sat on the road before being put in a police bus. The Congress leaders were later released after being in detention for several hours.

During today's questioning when her statement was recorded, Sonia Gandhi's response was sought to a set of around 30 questions pertaining to her involvement with the National Herald newspaper and Young Indian Pvt Ltd, the company under scanner in the case, officials said.

She was questioned for nearly 2.5 hours at the ED office in central Delhi from 11 AM which continued after a 90-minute lunch break before ending at around 7 PM.

The Congress chief had reached the ED office in the morning with her Z+ armed security cover, and was accompanied by Rahul Gandhi and Priyanka Gandhi Vadra.

While Priyanka stayed back at the ED office, Rahul left soon after to join the Congress protests.

Priyanka was in another room at the ED office so she could meet her mother to provide her medicines or medical assistance if necessary, officials said.

Sonia Gandhi was questioned for over two hours on July 21 during which she replied to 28 questions put forth by the agency. She had reiterated the Congress party stand that the Young Indian was a "not for profit" company and no personal benefits were gained by them.

The Lok Sabha MP from Rae Bareli was quizzed on Tuesday on the functioning and running of the newspaper, the role of its various office bearers, and her and Rahul Gandhi's participation in the affairs of the National Herald and Young Indian.

The agency will also corroborate her statement with that of Rahul Gandhi as both put together are majority stakeholders in Young Indian, officials said.

The questioning of the Gandhis pertains to the charge of alleged financial irregularities in the Congress-promoted Young Indian, which owns the National Herald newspaper.

The ED questioned Rahul Gandhi last month in sessions that clocked over 50 hours over five days.

The Congress has slammed the agency's action against its top leadership and termed it "political vendetta".

Delhi Police deployed a huge force, including CRPF and RAF personnel, and barricaded the entire over one kilometre stretch between her residence and the ED office. Traffic restrictions were also imposed in the area.

Rahul Gandhi and Congress MPs had gathered at the Vijay Chowk to march towards the Rashtrapati Bhavan to draw the President's attention to the alleged misuse of central agencies by the government, but were stopped by the police.

"I am not going anywhere. We wanted to go towards the President's house. But the police are not allowing us," Gandhi said.

"All Congress MPs stopped at Vijay Chowk and prevented from marching to Rashtrapati Bhavan. Forcibly arrested. Now we are in police buses being taken to a place only PM and HM know where ," Congress Rajya Sabha MP Jairam Ramesh tweeted.

"The Delhi Police harassed us. They have taken almost all the 75 MPs under detention and are taking them to unknown places," claimed Manickam Tagore.

The Delhi Police, meanwhile, said they are in the process of identifying the personnel who allegedly manhandled Indian Youth Congress president Srinivas BV during the protest by the Congress.

A video of Srinivas being pulled by his hair went viral on social media with several users condemning the police action. Deputy Commissioner of Police (New Delhi) Amrutha Guguloth said disciplinary action will be taken against the erring officials.

Srinivas alleged he was beaten up by three to four policemen before being detained.

The move to question the Gandhis was initiated after the ED late last year registered a fresh case under criminal provisions of the Prevention of Money Laundering Act(PMLA).

This was after a trial court here took cognisance of an Income Tax department probe against Young Indian based on a private criminal complaint by BJP MP Subramanian Swamy in 2013.

Sonia and Rahul Gandhi are among the promoters and majority shareholders in Young Indian. Like her son, the Congress president too has 38 per cent shareholding.

Swamy had accused the Gandhis and others of conspiring to cheat and misappropriate funds, with Young Indian paying only Rs 50 lakh to obtain the right to recover Rs 90.25 crore that Associate Journals Limited owed to the Congress.

In February last year, the Delhi High Court issued a notice to the Gandhis seeking their response to Swamy's plea.

Congress leaders Mallikarjun Kharge and Pawan Bansal were questioned by the ED in the case in April.

The Congress has maintained there has been no wrongdoing and Young Indian is a "not-for-profit" company established under section 25 of the Companies Act and hence there can be no question of money laundering.

It is understood that Rahul Gandhi, during his deposition before the ED, stuck to the position that there was no personal acquisition of assets by himself or his family.

According to the ED, assets worth about Rs 800 crore are "owned" by the AJL and the agency wants to know from the Gandhis how a not-for-profit company like Young Indian was undertaking commercial activities of renting out its land and building assets.