The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 128.78 crore in the futures & options segment on Thursday.According to data released by the NSE, FIIs were net sellers of index futures to the tune of Rs 87.58 crore and bought index options worth Rs 660.15 crore. They were net sellers of stock futures to the tune of Rs 464.87 crore and bought stock options worth Rs 21.09 crore.