MUMBAI, August 12: The Reserve Bank of India (RBI) on Tuesday said it had banned fresh purchases of shares of Mastek Ltd by foreign institutional investors (FIIs). "The overall ceiling of 30 per cent of paid up equity capital permitted to be held by all registered FIIs together with purchases made by all NRIs and OCBs under the portfolio investment scheme has already been reached in the case of Mastek Ltd," an RBI statement said.As per the existing regulations, FIIs can hold up to 30 per cent of the equity of a company provided the board of directors and shareholders approve the proposal.It may be recalled that FII holding in HDFC had crossed the 30 per cent limit and almost touched 33 per cent last week. RBI later hauled up custodians and brokers who purchased the additional equity in violation of RBI norms. FIIs who bought equity in excess of 30 per cent have been given time till October 31 to divest the stake.