Foreign institutional investors (FIIs) were net buyers of Rs 597.53 crore (provisional) on Thursday, according to data released by BSE. While FIIs made gross purchases of Rs 4,044.04 crore, gross sales totalled Rs 3,446.51 crore.Domestic institutional investors (DIIs) were net sellers of Rs 59.87 crore on Thursday. While DIIs made gross purchases of Rs 1,050.23 crore, gross sales totalled Rs 1,110.10 crore.