The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 1,320.55 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 1003.43 crore and bought index options worth Rs 241.79 crore. They were net buyers of stock futures to the tune of Rs 70.40 crore and bought stock options worth Rs 4.92 crore.As per data available on the Sebi website - FIIs were net sellers of stocks worth Rs 1,106.80 crore in the cash market on Wedneday. Mutual funds were net sellers of shares worth Rs 123.66 crore on the same day.