World oil prices moved higher, in part on fears the strike would disrupt Nigeria's exports.
Stores and office in Lagos, the sprawling commercial capital of sub-Saharan Africa's most populous nation, were barricaded shut for fear of looting. International and domestic controllers joined the protest.
Government offices and businesses in the capital, Abuja, the northern cities of Kano and Kaduna and the southeastern oil city of Port Harcourt were also closed.
In pamphlets, the striking Nigeria Labor Congress urged the public to ransack any businesses that opened despite the strike.
"Fast food joints, all markets, shops and stores ... are offering their commodities free. Enter and pick your choice," the leaflets declared.
"Cars and buses on the road are for the strike. Stop them and enter free," the labor congress declared. "If any driver resist, drive it yourself."
Labor Congress leader Adams Oshiomole insisted the strike would continue indefinitely despite a ruling by a Lagos court Friday declaring the action illegal.
Ufot Ekaette, the government secretary, warned Sunday that civil servants participating in the protest faced possible dismissal.
Riot police fired tear gas at hundreds of civil servants blocking the entrance to a federal government office block in Abuja.
In the Lagos working-class neighborhoods of Yaba, Ikeja and Surulere, police lobbed tear gas and fired bullets in the air to disperse chanting union members and gangs of thugs who burned tires and other debris on rubbish-strewn streets. Known as "area boys," the gangs wielded nail-studded clubs and machetes and extorted money from the few motorists venturing out.
The protest comes after the government raised gasoline, kerosene and diesel prices by more than 50 percent on June 20. Officials said the fuel hike was necessary to end shortages and curb smuggling of cheap Nigerian fuel to neighboring countries.
Union leader Adams Oshiomole said the fuel hike was causing great hardship for millions of Nigerians earning $1 a day or less.
"We don't want a Nigeria where only the rich can survive. That's why we will fight this battle to the bitter end," Oshiomole told cheering supporters in a speech cut short by police firing tear gas.
Nigeria is Africa's largest oil exporter and the fifth-largest source of U.S. oil imports. Yet union leaders argue that low fuel prices have been among the only benefits enjoyed by the impoverished majority.
Multinational oil company headquarters in Lagos were closed after Nigeria's largest blue-collar oil workers' union joined in the strike. The white-collar union said some of its members were also participating.
A spokesman for Shell, Nigeria's largest oil company, said the protest was not affecting oil production or exports. The official spoke to The Associated Press on condition of anonymity.
"It may not effect oil exports immediately," said Sina Luwoye, president of the white-collar union. "But in a couple of days we may see the effect."
Oil prices rose Monday, in part because of the Nigeria strike. Volume of trading was low, with many traders waiting to see the protest's effect on oil exports.
Nigeria, with 126 million people from 250 ethnic groups, is riven by political, religious and ethnic tensions that frequently explode into violence killing more than 10,000 people since President Olusegun Obasanjo was first elected in 1999, ending decades of brutal military rule.