India have protested to London Olympic organisers after a mysterious woman gatecrashed their squad at the opening ceremony, media reports said on Sunday.

The unidentified woman, dressed in a red top and blue pants, was seen walking alongside India's flag-bearer Sushil Kumar at Friday's ceremony even though she was not part of the contingent.

India's acting chef-de-mission Muralidharan Raja slammed the intrusion, but stopped short of calling it a security breach even though the woman was not wearing the customary identification badge.

"She had no business being there. It was a clear case of intrusion," Raja was quoted as saying by the Times of India. "We are taking up the issue with the organisers.

"We don't know who she is and why she was allowed to walk in. It is a shame that she was walking with our athletes.

"I can't say that (if it was a security breach) as she was in a sanitised zone, but this was bizarre. We will ask for an apology.

"She embarrassed us in front of the world. The Indian contingent was shown (on television) for just 10 seconds, and to think this lady hogged all the limelight."

Raja, asked if he believed the woman was an Indian, said: "She could be Asian, Latin American, I don't know."

India has fielded its largest Olympic contingent of 81 athletes with hopes of bettering its Beijing Games tally of one gold and two bronze medals.