The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 699.49 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 579.56 crore and bought index options worth Rs 4.31 crore. They were net buyers of stock futures to the tune of Rs 118.59 crore while sold stock options worth Rs 2.97 crore.As per data available on the Sebi website - FIIs were net sellers of stocks worth Rs 861.40 crore in the cash market on Wednesday. Mutual funds net buyers of shares worth Rs 38.22 crore on the same day.