Many Nigerian shops and offices are closed at the start of a four-day general strike over fuel price rises in Africa's largest oil producer.
Fuel price rises have hit many Nigerians very hard
The strike call has been followed in the main cities of Abuja and Lagos but oil production has not been affected.
The strike is one reason why world oil prices have reached a new record high.
Despite Nigeria's oil wealth, most of the population lives in poverty and many see cheap fuel as the only benefit they receive.
Fuel subsidies were removed last year, leading to large increases in the price of petrol.
On Monday morning, prices of Brent crude oil passed the $50 a barrel mark for the first time.
Police have been put on alert across Nigeria and one person has been shot and injured in the northern city of Kaduna when they dispersed protesters who had attempted to close roads in support of the stayaway.
On Monday morning, most shops, offices and petrol stations in Nigeria's largest city, Lagos, were closed, and there was much less traffic than usual.
But some market traders opened in the afternoon. The BBC's Anna Borzello in Lagos says that many Nigerians support the idea of a strike but cannot afford not to work.
The strike was also well observed in the capital, Abuja.
In a bid to take the steam out of the strike, President Olusegun Obasanjo has set up a task force to look at the effects of the fuel price rises, which includes the leader of Nigeria's trade union umbrella group, Adams Oshiomhole.
A spokesman for the Nigeria Labour Congress told the BBC that Mr Oshiomhole would go along to find out what the government had to say.
But he added that the strike would only end if the recent 25% hike in petrol prices is reversed.
Seeking final deal
The unions are ignoring a court order issued last month, which banned them from striking for reasons other than working conditions.
Mr Oshiomhole said after four days, the action would be suspended to give the government the opportunity to change its position and start talking to the unions.
He told the BBC that he wanted to persist with union action to resolve the matter once and for all.
"If they talk and we are able to resolve the issues, then that is the end of it," he told the BBC's Focus on Africa programme.
"If they don't, then after two weeks we will resume the strike... This time we have to pursue this until there is a final deal that is acceptable to all".
Mr Oshiomhole - who leads the 29-union umbrella body - has led two widely observed general strikes in the last 18 months over fuel price increases.
The union leader was detained on Saturday in Abuja.
Mr Oshiomhole said he was picked up by state security service operatives on the tarmac of the domestic airport, as he was about to board a plane.
Oshiomhole said he had been manhandled
He said the 15-men strong security service team wanted him "to follow them to their boss" without producing any warrant.
After he refused to go, he said he was treated "very rough" by the officers.
"They started pushing me... they tore my suit, my jacket... and they forced me into the car," said Mr Oshiomhole.
The state security services say Mr Oshiomhole was allowed to go home on Saturday, after answering questions over what they describe as a misunderstanding with field operatives.