Stocks of three state-owned oil marketing companies (OMCs) tanked by as much as six per cent on Wednesday following reports that the government was mulling placing curbs on their newly acquired powers to determine transport fuel prices on a daily basis. According to market observers, the slide in OMC scrips followed reports that the Government proposed to curb the pricing powers of OMCs in view of the steep hike in the cost of petroleum products over the past almost three months, even though international crude oil prices have remained stable. The selling pressure in OMCs' stock prices also dragged the benchmark indices -- BSE Sensex and NSE Nifty -- lower. “Most Indian equity benchmarks declined as shares of oil marketers sold off on reports that the government may ask these companies to absorb fuel price increase,” Dhruv Desai, Director and COO of Tradebulls said.