Shares of Oil and Natural Gas Corporation (ONGC) rallied 5 per cent to Rs 172.65 on the BSE in Monday’s intra-day trade in an otherwise weak market on the back of rising crude oil prices. At 10:40 am; the stock was up 4 per cent around Rs 171.80-odd levels, as compared to a 3.2 per cent decline on the S&P BSE Sensex.