The Foreign Institutional Investors (FIIs) were net buyers to the tune of Rs 687.82 crore in the futures & option segment on Wednesday.According to data released by the NSE, FIIs were net buyers of index futures to the tune of Rs 364.71 crore and bought index options worth Rs 244.09 crore. They were net buyers of stock futures to the tune of Rs 79.03 crore.As per data available on the Sebi website - FIIs were net buyers of stocks worth Rs 139 crore in the cash market on Tuesday. Mutual funds were net sellers of shares worth Rs 78.81 crore on the same day.