India is fuming over the presence of a mystery woman who led out the nation's athletes at the opening ceremony.

The Times of India reports that the woman "brazenly" walked alongside the official flag bearer, Sushil Kumar, yet no-one knows who she was or how she came to be at the head of the group.

And she was not even dressed in team attire.

India's 40 athletes and 11 officials were dressed in yellow turbans and sarees, while the mystery woman was in jeans and a red zip-up jumper.

The incident has raised serious security concerns and the Times quotes Indian officials as being utterly in the dark about how it happened.

"She had no business being there. It was a clear case of intrusion," Acting Chef de Mission Brig P K M Raja is quoted as saying.

"We are taking up the issue with the organisers. We don't know who she is and why she was allowed to walk in."

The Indian delegation is also demanding an apology from LOCOG.