The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 320.72 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 82.89 crore and bought index options worth Rs 103.46 crore. They were net buyers of stock futures to the tune of Rs 135.26 crore while sold stock options worth Rs 0.90 crore.As per data available on the Sebi website - FIIs were net buyers of stocks worth Rs 23.30 crore in the cash market on Tuesday. Mutual funds were net buyers of shares worth Rs 561.20 crore on the same day.