Washington: Citing what it called "hidden intelligence breakdowns" behind the 2008 Mumbai terror attacks, a new investigative report has described Mumbai "as a tragic case study in the strengths and limitations of high-tech surveillance".

An analysis of documents leaked by Edward Snowden contradicted the US government's claims that the National Security Agency had played a key role in preventing a follow-up plot against a Danish newspaper in 2009, says the report by Sebastian Rotella.