Sebi Tuesday asked the National Stock Exchange to pay more than Rs 600 crore for the misuse of its co-location facility.

The market regulator, which probed alleged lapses in high-frequency trading offered through NSE's co-location facility. asked the bourse's two former chief executive officers -- Ravi Narain and Chitra Ramkrishna --to disgorge 25 per cent of their salaries drawn during a certain period.

Narain and Ramkrishna have been prohibited from "associating with a listed company or a Market Infrastructure Institution or any other market intermediary for a period of five years," Sebi said in a 104-page order.

NSE has also been prohibited from accessing the securities market directly or indirectly for six months.

The bourse "shall disgorge an amount of Rs 624.89 crore... along with interest calculated at the rate of 12 per cent per annum from April 1, 2014 onwards to the Investor Protection and Education Fund (IPEF) created by Sebi," the order said.