Jane Street has told staff it will contest a ban by India's financial regulator which has accused the U.S. high-frequency trading giant of market manipulation, adding that its practices in question were "basic index arbitrage trading".

On Thursday, Sebi issued an interim order barring the U.S.-based investment firm and its group entities from accessing the securities market in India, while directing them to disgorge ₹4,843.57 crore in alleged unlawful gains.

A study by the Securities and Exchange Board of India found that retail investors lost more than $20 billion on option trades over three years. On July 4, SEBI announced it would seize 48.4 billion rupees ($570 million) from trading giant Jane Street Group,