The foreign institutional investors (FIIs) were net buyers to the tune of Rs 922.31 crore in the futures & option segment on Tuesday.According to data released on the NSE website, FIIs were net buyers of index futures to the tune of Rs 789.86 crore and they bought index options worth Rs 183.45 crore. They were net buyers of stock futures to the tune of Rs 135.84 crore while they sold stock options worth Rs 3.39 crore.As per data available on the Sebi website - FIIs were net buyers of stocks worth Rs 31.50 crore in the cash market on Thursday. Domestic mutual funds (MFs) were net buyers of shares worth Rs 88.62 crore on the same day.