The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 841.84 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 768.10 crore and bought index options worth Rs 325.79 crore. They were net sellers of stock futures to the tune of Rs 237.75 crore and sold stock options worth Rs 14.30 crore.As per data available on the Sebi website - FIIs were net buyers of stocks worth Rs 363.50 crore in the cash market on Wednesday. Mutual funds were net sellers of shares worth Rs 332.20 crore on the same day.