LAGOS, March 2 (Reuters) - Queues for fuel formed across Nigeria on Tuesday over fears of a rise in gasoline costs, even as the state oil company promised consumers that prices would remain stable. Lines of cars waiting to enter petrol stations snarled the traffic in Lagos, the packed commercial capital, while some stations in the capital Abuja stopped selling fuel for fear of losing money if prices rose. Nigeria said last year it had liberalized the sector, and eliminated costly subsidies. But state oil company NNPC has acknowledged it remains the sole gasoline importer. It is also setting prices at fuel depots. In a statement on Tuesday, fuels regulator the Department of Petroleum Resources warned sellers against hoarding fuel. “The DPR will not hesitate to apply appropriate sanctions on any outlet found wanting in this regard,” DPR director Sarki Auwalu said in the statement. “The regulatory agency has set up a special taskforce to intensify surveillance and monitoring of all retail outlets and depots nationwide.” On Monday, state oil company NNPC said it had ruled out price increases in March while its negotiations with organized labour over fuel prices continued. It also cautioned against “artificial scarcity”. Experts said the decision not to increase prices, even as global gasoline became more expensive, meant the government was incurring subsidy costs. (Reporting By Libby George in Lagos, Camillus Eboh in Abuja and Tife Owolabi in Yenagoa; editing by David Evans)