The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 697.91 crore in the futures & option segment on Thursday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 527.69 crore and bought index options worth Rs 246.87 crore. They were net sellers of stock futures to the tune of Rs 64.49 crore and sold stock options worth Rs 12.15 crore.As per data available on the Sebi website - FIIs were net sellers of stocks worth Rs 6.20 crore in the cash market on Wednesday. Mutual funds were net sellers of shares worth Rs 274.92 crore on the same day.