Nigerian authorities have scrapped fuel subsidies with immediate effect - a policy expected to push up petrol prices.
The move has prompted unions to call for mass strikes and street protests.
Nigerians view the subsidy as their only benefit from the nation's oil wealth.
Many fuel stations in the capital Abuja and main commercial city Lagos were shut today while they waited to figure out how to adjust their prices.
Those that were open were jammed with queues and selling at prices of up to 150 naira (€0.71) per litre, up from a fixed price of 60 naira (€0.28) before.
Economists and government officials, however, view removing the subsidy as essential to allow for more spending on the country's woefully inadequate infrastructure and as a way to ease pressure on its foreign reserves.
The government says more than €6 billion was spent in 2011 on fuel subsidies.
While the government has been discussing the subsidy removal for weeks, there was no prior warning to the public that it would occur on 1 January.
A statement by the Petroleum Products Pricing Regulatory Agency (PPPRA) announced the "formal removal of the subsidy on Premium Motor Spirit".
"Petroleum products marketers are to note that no one will be paid a subsidy on PMS discharges after 1st January 2012," said the statement signed by the agency's executive director, Reginald Stanley.
The Trades Union Congress and Nigerian Labour Congress called for mass action in response.
"We alert the populace to begin immediate mobilisation towards the D-Day for the commencement of the strikes, street demonstrations and mass protests across the country," they said in a joint statement.
Nigeria refines very little of its crude despite being a major oil producer - a situation blamed on corruption and mismanagement.
Therefore, it must import fuel even while it exports crude.
Subsidies are supposed to keep pump prices low even though fuel is being imported at market prices, but there have been serious questions over how the subsidy cash has been paid out.
There have been accusations that much of the money goes to a handful of corrupt elites. Fuel is also sold above the set price in many areas outside of major cities.
The announcement comes at a difficult time for the country - a day after President Goodluck Jonathan declared a state of emergency in areas of the country hard-hit by Islamist attacks.
