NEW YORK (REUTERS) - The US attorney in Manhattan has defended the treatment of an Indian diplomat who was strip-searched after her arrest last week on charges of underpaying her nanny, a case that has strained US-Indian relations.

Manhattan US Attorney Preet Bharara, in an unusually lengthy written statement in a pending case, said on Wednesday he wanted to clear up the "misinformation" surrounding the arrest of diplomat Devyani Khobragade, and he questioned why there was more sympathy for Dr Khobragade than her alleged victim.

"Ms Khobragade was accorded courtesies well beyond what other defendants, most of whom are American citizens, are accorded," Mr Bharara said, adding that his sole motivation was to "hold accountable anyone who breaks the law - no matter what their societal status and no matter how powerful, rich or connected they are."

He said Dr Khobragade had been "fully searched" by a female deputy marshal after her arrest.

"This is standard practice for every defendant, rich or poor, American or not," said Mr Bharara, who was born in India, raised in New Jersey and has built a reputation as "The Sheriff of Wall Street" for his prosecution of insider trading cases.

India has been furious about what it considers the degrading treatment of a senior diplomat by the United States, a country it sees as a close friend, and retaliated on Tuesday by removing security barriers at the US Embassy in New Delhi. The barriers would offer some protection against a suicide bomb attack.

Mr Bharara's statement came after US Secretary of State John Kerry discussed the case with Indian National Security Adviser Shivshankar Menon. Mr Kerry called to express regret about the case and his concern it not hurt the two countries' relationship, the State Department said on Wednesday.

"As a father of two daughters about the same age as Devyani Khobragade, the secretary empathises with the sensitivities we are hearing from India about the events that unfolded after Ms Khobragade's arrest," State Department spokeswoman Marie Harf said in a written statement.

Dr Khobragade was released on US$250,000 (S$314,000) bail after giving up her passport and pleading not guilty to charges of visa fraud and making false statements about how much she paid the housekeeper.

She faces a maximum of 15 years in jail if convicted of both counts.

The US Justice Department confirmed that Dr Khobragade was strip-searched after her arrest. A senior Indian government source has also said the interrogation included a cavity search.

A spokeswoman for the US Marshals Service, Nikki Credic-Barrett, said Dr Khobragade did not undergo a cavity search but did go through a strip search. Under the agency's regulations governing prisoner searches, a strip search can include a "visual inspection" of body cavities, including the nose, mouth, genitals and anus, without intrusion.

Dr Khobragade told colleagues in an email of "repeated handcuffing, stripping and cavity searches, swabbing" and being detained in a holding cell with petty criminals, despite her "incessant assertions of immunity."

While common in the United States, jail strip searches have prompted legal challenges from civil liberties groups concerned that the practice is degrading and unnecessary.

Ezekiel Edwards, an attorney with the American Civil Liberties Union, said that despite a Supreme Court ruling last year upholding strip searches even in the absence of any suspicion the individual has contraband or weapons, law enforcement authorities should make an effort to distinguish between prisoners who merit invasive searches and those who pose no risk.

"Saying that it's not unusual is not to say that it should be acceptable," he said.

Mr Bharara denied media reports that Dr Khobragade had been arrested in front of her children. "The agents arrested her in the most discreet way possible, and unlike most defendants, she was not then handcuffed or restrained," he said.

Officers allowed her to make calls, including to arrange child care, and even brought her coffee, the prosecutor said.

Mr Bharara said Dr Khobragade clearly tried to evade US law designed to protect from exploitation the domestic employees of diplomats and consular officers.

"One wonders why there is so much outrage about the alleged treatment of the Indian national accused of perpetrating these acts, but precious little outrage about the alleged treatment of the Indian victim and her spouse?" he said.

The Indian housekeeper whose paycheck is at the centre of the dispute, Sangeeta Richard, is said to be upset and disappointed the focus of the affair has shifted.

"The victim in this case is not a criminal defendant but the person who was denied her wages and underpaid for her work," said Dana Sussman, an attorney with the Safe Horizon Anti-Trafficking Program who is representing Ms Richard.

Dr Khobragade falsely stated in her nanny's visa application that she would be paid US$9.75 an hour, a figure that would have been in line with the minimum rates required by US law, according to a statement issued last week by Mr Bharara.

The diplomat had privately agreed with the domestic worker that she would receive just over a third of that rate, the US attorney said.

Ms Harf, the State Department spokeswoman, said Mr Kerry had used the word "regret" in his conversation with Mr Menon, but she declined to elaborate on whether this constituted an apology or to offer greater detail on their discussion.

An expression of regret, in the world of diplomacy, is generally viewed as something short of an outright apology.

White House spokesman Jay Carney said the administration is looking into the arrest "to ensure that all standard procedures were followed and that every opportunity for courtesy was extended."

The White House has told Indian officials it expects New Delhi will "fulfil all its obligations" for the safety and security of US diplomats in India, Mr Carney said.

India has appointed Dr Khobragade to its permanent mission at the United Nations and her attorney Daniel Arshack said that, in her new role, she would have diplomatic immunity from prosecution retroactively.

However, the State Department would have to sign off on a request to move her from the consulate to the UN mission, and no such request has been received, Ms Harf told reporters. She said the US government notified India of the allegations against Dr Khobragade in September.

India and the United States have become close trade and security partners, but they have not totally overcome a history of distrust.

"It is no longer about an individual, it is about our sense of self as a nation and our place in the world," Foreign Minister Salman Khurshid told parliament, whose usually fractious members showed rare unity on the issue.

Mr Khurshid said work conditions of Indians employed in US consulates would be investigated to root out any violations of labour laws, adding that there would be a freeze on the duty-free import of alcohol and food for diplomatic staff.

In New Delhi, supporters of a right-wing opposition party held a small protest near the US Embassy on Wednesday. About 30 demonstrators, some wearing masks of President Barack Obama and sarongs made from the US flag, demanded an apology.

The controversy over Dr Khobragade's experience is not the first time that overseas observers have been horrified at the treatment of a foreign criminal defendant in the United States.

In 2011, when then-International Monetary Fund chief Dominique Strauss-Kahn was paraded before TV cameras in handcuffs during what is known in the United States as a "perp walk", or perpetrator walk, after being arrested in New York on charges of sexual assault, French media reacted with shock.

Prosecutors ultimately dropped the charges.

In France, the presumption of innocence legally bars the media from showing defendants in handcuffs before they are convicted.

The Khobragade case is the latest concerning the Indian elite's alleged exploitation of their domestic workers, both at home and abroad.

Another official at India's consulate in New York was fined almost US$1.5 million last year for using her maid as forced labor. Last month, the wife of a member of parliament was arrested in Delhi for allegedly beating her maid to death.

India says Dr Khobragade's former housekeeper left her employer a few months ago and demanded help to obtain permanent resident status in the United States.

One Indian government minister, Shashi Tharoor, has argued that it is not reasonable to expect diplomats from developing countries to pay the US minimum wage to domestic staff because the envoys themselves earn less than that.