A mysterious woman in red has caused an international incident at the London Olympics.

Indian officials are mystified after an unknown woman managed to march with the country's athletes and officials during the opening ceremony on Friday night.

Images from the ceremony showed the woman marching alongside Indian flag bearer Sushil Kumar at the head of the delegation of 40 athletes.

The country's Deccan Chronicle newspaper said she was likely Madhura Nagendra, a graduate student from the southern city of Bangalore who had been living in London.

In the meantime organising chief Sebastian Coe insisted the woman had not posed a threat to the ceremony saying the interloper was a ceremony cast member and had been screened before entering the Olympic Park.

Some 10 thousand volunteers performed alongside professional musicians, actors and dancers in the opening ceremony.