The US National Security Agency targeted the Indian embassy in Washington and the Indian UN office in New York with sophisticated surveillance equipment that might have resulted in hard disks being copied, a report said on Wednesday.
The Hindu newspaper, which has been collaborating with the Guardian newspaper reporter Glenn Greenwald, said the Indian offices were on a top-secret list of countries chosen for intensive spying.
The NSA "selected India's UN office and the embassy as (a) 'location target' for infiltrating their computers and telephones with hi-tech bugs," the paper said, citing a secret internal document from the spy agency.
It said India's missions were marked for various snooping techniques including one codenamed "Lifesaver" which "facilitates imaging of the hard drive of computers."
India and the US have put past difficulties behind them and become firm allies over the last decade, with Prime Minister Manmohan Singh set to meet US President Barack Obama in Washington on Friday.
The revelations about US spying activities, leaked through documents obtained by former NSA contractor Edward Snowden, have already strained relations between Obama and his foreign allies, notably Brazilian President Dilma Rousseff.
The Hindu's report gives more detail on previous revelations published in the Guardian by Greenwald in July, that 38 embassies and diplomatic missions were targeted by the NSA, including India's.
New Delhi has previously defended widespread snooping on Internet users and phone calls by US intelligence agencies, saying such scrutiny had helped prevent "terrorist attacks."
But the foreign ministry expressed concern about suspected spying on its diplomatic missions in July and said it would raise the issue with US authorities.
The new revelations are likely to lead to calls from the opposition in India for the government to take a firmer line with Washington.