One protester has been killed as thousands of Nigerians have demonstrated against the removal of a fuel subsidy, which has led petrol prices and transport fares to double.
Officials say the man was killed by "mob action" in Kwara state, while witnesses say he was shot by police as they tried to disperse protesters.
There were marches in Lagos and other cities around the country.
Nigeria is Africa's biggest oil producer, but imports refined petrol.
Police fired tear gas at youths in the commercial capital, Lagos, after they blocked main roads, set up burning barricades and tried to force petrol stations to close.
However, the BBC's Tomi Oladipo in the city says the main march passed off peacefully, with demonstrators chanting anti-government slogans.
Analysts say many Nigerians regard cheap fuel as the only benefit they get from the nation's oil wealth.
Nigeria's trade unions have said they will call a strike and are meeting on Wednesday to decide on the plans.
Police block protests
Tuesday is the first working day since the measures were announced on 1 January.
The demonstrator was killed in Kwara's state capital, Ilorin.
There have been protests in numerous parts of the country, including Lagos, Ibadan, Lokoja, Nasarawa and Kano, where about two dozen people were arrested as they gathered.
Our reporter in Lagos says the city is not as busy as it normally is, with many people stranded as they cannot afford the new transport fares after going away for the holidays.
Police in the capital, Abuja have blockaded Eagle Square, where protesters had planned to gather.
On Monday, police fired tear gas to disperse some 200 people who had gathered in the capital, chanting: "Remove corruption, not subsidy."
Prices have increased from 65 naira ($0.40; £0.26) per litre to at least 140 naira in filling stations and from 100 naira to at least 200 on the black market, where many Nigerians buy their fuel.
There are reports that petrol prices have tripled in some remote areas, while commuters have complained that motorcycle and minibus taxi fares have already doubled or tripled.
Many Nigerians expect the prices of other goods to rise as well.
The government has said it will spend the money saved by removing the subsidy on improving the country's erratic electricity supply, as well as health and education.
However, analysts say that many Nigerians have little faith that the money will be well spent and fear it will instead be stolen by corrupt officials.
In December, the government released a list of the people who benefit most from the subsidy, which include some of Nigeria's richest people - the owners of fuel-importing firms.
Years of mismanagement and corruption mean Nigeria does not have the capacity to refine oil into petrol and other fuels.
Several previous governments have tried to remove the subsidy but have backed down in the face of widespread public protests and reduced it instead.
The IMF has long urged Nigeria's government to remove the subsidy, which costs a reported $8bn (£5.2bn) a year.