The Nigeria Labour Congress (NLC) announced the strike after the government raised fuel prices by 67%.
It is not immediately clear how widely the strike is being observed. Public schools in Abuja remain open.
Banks, markets and many government offices are also open and there is heavy traffic on the capital`s roads.
Another union grouping, the Trade Union Congress, earlier said it was suspending strike action by its members.
And it was unclear how many NLC members were joining the strike.
The BBC`s Chris Ewokor in Abuja said one NLC faction, which includes workers in the oil and gas sector, opposed the strike and was not planning to take part.
One member of that group, Joe Ajaero, told AFP news agency: "We have asked the government to cushion the effects of the price increase on the people as well as make petrol readily available.
"[The] government has to increase the minimum wage... because of the multiplier effects of the petrol price hike on foodstuffs, goods and services."
Nigeria unions pressing ahead with strike despite court ruling
18 May 2016
Read: 748
Nigeria`s main trade union federation is pressing ahead with a general strike, despite a court injunction against the action.
-1780923278.jpg&h=190&w=280&zc=1&q=100)
