Foreign institutional investors (FIIs) were net buyers of Rs 276.60 crore on September 19, Tuesday according to data released by Sebi today.While FIIs made gross purchases of Rs 1540.70 crore, gross sales totalled Rs 1264 crore.Mutual funds (MFs) were net buyers of Rs 127.28 crore on Tuesday. MFs made purchases of Rs 430.94 crore and sales of Rs 303.66 crore.