A New York grand jury on Friday re-indicted an Indian diplomat accused of mistreating her housekeeper on two counts of visa fraud and making false statements, threatening to reignite a bitter row with New Delhi.

The announcement from the Manhattan federal prosecutor came two days after a US judge threw out a previous case on the grounds that the former consular official was granted full diplomatic immunity after her arrest.

But the new, 21-page indictment paints a devastating picture of the lengths to which Devyani Khobragade allegedly went to infringe US laws in hiring a nanny-cum-housekeeper when she moved to New York in 2012.

Khobragade was arrested on December 12 outside her children's school and later strip-searched, enraging the Indian government and some of the Indian public.

The diplomatic row between the two countries, which had embraced each other as strategic partners, strained ties and fanned resentment on both sides.

US prosecutors, disputing her immunity, accuse Khobragade of forcing her Indian maid to work 100 hours or more a week, even when sick and without a full day off, for $1.42 or less an hour.

The indictment accuses Khobragade of presenting false information to obtain a visa for her housekeeper and coaching her to lie to US Embassy officials.

It says the Indian diplomat drew up a fake contract that conformed with US labor law but made her employee sign another contract the night they boarded a flight to New York in November 2012.

The second contract stipulated a salary of $573 a month or $6,876 a year without overtime and the legal protections she was owed in the United States.

The housekeeper worked from 6:30 am to as late as 9:30 pm or even midnight Monday to Saturday, the indictment says, and four hours on Sunday.

It also accuses the diplomat of trying to silence and intimidate the housekeeper, who fled in June 2013 after she protested her conditions.

The diplomat's lawyer Daniel Arshack refused to comment on the re-opening of the case.

"The government of India will respond in due course," he said in a statement to AFP.

- Limited immunity -

Employed as a deputy consul general at the consulate in New York, Khobragade obtained in January the full immunity granted to diplomats at the Indian mission to the UN.

It was on those grounds that she petitioned a US court on January 9 to drop the case, before flying back to India, where she now works for the foreign ministry.

On Wednesday, US District Judge Shira Scheindlin dismissed the original indictment on the grounds that Khobragade was granted full diplomatic immunity the day before she left, on January 8.

But the office of Preet Bharara, the US attorney for the Southern District of New York, then said it intended to re-charge the diplomat.

The court had only found that Khobragade had immunity "during a limited period of time between January 8 and January 9, when the current indictment was returned by a grand injury," Bharara's spokesman said.

"As the court indicted in this decision, and as Devyani Khobragade has conceded, there is currently no bar to a new indictment against her for her alleged criminal conduct, and we intend to proceed accordingly."

India had welcomed the dismissal of the case, but the US State Department reserved judgment.

"We were surprised by the dismissal of the indictment against former Indian Deputy Consul General Devyani Khobragade," spokeswoman Jen Psaki told reporters.

Khobragade's father had thanked New Delhi for rallying behind the family and lashed out at the US for trying to frame his daughter in a "false" case.

His daughter, who returned to India in January to a hero's welcome, has told a local newspaper about her anguish in leaving behind in New York her two young daughters and her husband, a US citizen and academic.