The public sector undertaking (PSU) stocks gained between 1 per cent and 7 per cent on reports that the government plans fast-track disinvestment of three firms and aims to complete the process by the end of the current financial year. Rural Electrification Corporation (REC) was up 5 per cent to Rs 252.50, NMDC was up 3.6 per cent to Rs 434 and NTPC was up 1 per cent to Rs 233.10 on BSE.