New Delhi, July 31 -- High-frequency traders or HFTs, among the top liquidity providers for index options, have curbed their activity and are in a "wait and watch" mode after the market regulator cracked down on US hedge fund Jane Street and rolled new position limits for derivatives, according to the National Stock Exchange's top executive.

"Jane Street naturally is a revelation to many, and currently is more a surveillance matter, which we don't discuss," said Ashishkumar Chauhan, managing director and chief executive officer of NSE, during an investor conference call on Wednesday, a day after the bourse announced its first quarter earnings.

"Even I am not privy to that because it's between our surveillance department and Sebi, but ba...