India's foreign ministry has protested to Washington after reports two of New Delhi's diplomats were frisked at U.S. airports, describing the searches as serious breaches of protocol. Hardeep Puri, India's ambassador to the United Nations, was subjected to a pat-down search and held for 30 minutes at Houston airport a fortnight ago after refusing on religious grounds requests by officials to remove his turban, the Press Trust of India news agency reported on Monday.

On December 4, Indian ambassador to the United States Meera Shankar was selected by security officials at a Mississippi airport for a pat-down search, despite reportedly notifying officials of her diplomatic status.

"We have taken it up with the U.S. authorities and the matter is at that stage," External Affairs Minister S.M. Krishna said on Monday, referring to Puri, a Sikh.

Sikh men keep their hair covered at all times with a turban, which is not allowed to be touched in public.

The searches sparked off outrage in India, with several political parties demanding U.S. officials too be frisked at Indian airports. India exempts holders of diplomatic passports from airport searches. "Let me be frank. This is unacceptable to India. We are going to take it up with the government of the United States so that such unpleasant incidents do not recur," Krishna told reporters on Thursday in response to the Shankar incident.

There have been past instances of Indian officials at U.S. airports being searched, but beyond New Delhi issuing protests, they have not caused any major diplomatic row.

Last year, Continental Airlines frisked former Indian President Abdul Kalam. Then-Indian defense minister George Fernandes was strip-searched twice at a Washington airport in 2002 and 2003. The U.S. Homeland Security Department had initially described Shankar's pat-down as "appropriate under the circumstances" before Secretary of State Hilary Clinton on Thursday said she was "concerned" and an official apology was issued.

"Secretary of State Hilary Clinton has indicated that they have to revisit some of their procedures particularly with reference to the diplomatic corps of other countries," Krishna told NDTV on Monday. (Reporting by Henry Foy; Editing by C.J. Kuncheria)