Foreign institutional investors (FIIs) were net buyers of Rs 639.68 crore (provisional) on Friday, according to data released by BSE.While FIIs made gross purchases of Rs 2,758.22 crore, gross sales totalled Rs 2,118.54 crore.FIIs were net sellers of Rs 359 crore on Thursday, March 29, according to data released by Sebi on Friday. While FIIs made gross purchases of Rs 4,050.20 crore, gross sales totalled Rs 4,409.20 crore.Mutual funds (MFs) were net sellers of Rs 60.01 crore on Thursday. MFs made purchases of Rs 522.13 crore and sales of Rs 582.14 crore.