US authorities have been asked to investigate allegations that hackers India used back-door codes provided by companies to spy on private exchanges by a US commission on China, an official said Tuesday.

A hacker group calling itself the Lords of Dharmaraja released excerpts of documents that it said were part of an Indian intelligence unit's surveillance of the US-China Economic and Security Review Commission.

"We are aware of these reports and have contacted relevant authorities to investigate the matter," commission spokesman Jonathan Weston said. He declined further comment.

The commission, which consists of 12 experts, was set up by Congress in 2000 to monitor the security implications of US trade with China. It publicly releases findings and recently produced an extensive study on alleged Chinese cyber-espionage.

The email exchanges released by the hackers showed the commissioners discussing their wording on issues such as arms sales to Taiwan and China's currency valuation but did not appear to contain bombshells.

However, a purported document on Indian military letterhead states that spies were able to access the exchanges through a "backdoors" method made available to Indian authorities by communication companies.

"Decision was made earlier this year to sign an agreement with mobile manufacturers in exchange for the Indian market presence," said the alleged document dated October 6.

It specifically names BlackBerry smartphones' Canadian maker Research In Motion (RIM), US tech giant Apple and Finnish mobile manufacturer Nokia.

It was not possible to verify independently the authenticity of the document, which unclearly speaks of authorization for the operation by "the President."

Representatives from the companies and the Indian embassy in Washington did not immediately respond to requests for comment.

India a year ago resolved a prolonged standoff with RIM after authorities complained that terrorists could use encrypted BlackBerry messages.

BlackBerry said in January 2011 it would allow the Indian government to monitor BlackBerry messenger and public email services, but not corporate emails.

India has uneasy relations with fellow Asian giant China. India recently lodged a protest after two of its nationals alleged that they were tortured in a hotel room over a business dispute in the city of Yiwu.

Relations also remain tense over a border dispute and India's welcoming of thousands of Tibetans who fled Chinese rule, including the Dalai Lama.