The foreign institutional investors (FIIs) were net buyers to the tune of Rs 810.78 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 962.43 crore while they sold index options worth Rs 5.80 crore. They were net sellers of stock futures to the tune of Rs 153.78 crore while they bought stock options worth Rs 7.92 crore.As per data available on the Sebi website - FIIs were net buyers of stocks worth Rs 236 crore in the cash market on Wednesday. Mutual funds (MFs) were net sellers of shares worth Rs 269.32 crore on the same day.