Nigeria's main oil workers union threatened to shut down the country's oil industry as a nationwide general strike entered its third day Wednesday, increasing concerns about supply from Africa's biggest crude producer.

A general strike in protest against high local fuel prices began Monday, following a series of price hikes triggered by last year's deregulation of the fuel market.

The strike has not so far affected oil supply from Nigeria, but such fears have helped send world oil prices to record levels.

The president of Nigeria's largest oil workers union, NUPENG, said Tuesday its members were still working at key positions for the time being but vowed to shut down production if the government used heavy-handed tactics to end the protest.

"If nothing serious happens, we will maintain this position," Peter Akpatason told The Associated Press. "But if there are arrests, we will change our strategy ... We can move to stop operations 100 percent."

A nation of over 130 million, Nigeria is the world's seventh-largest oil exporter and the fifth-biggest source of U.S. oil imports.

Nigeria's leading trade union, the Nigeria Labor Congress (search), which is spearheading the general strike, threatened to extend its duration. The action was supposed to last four days, then resume again in two weeks if fuel prices don't come down.

Labor Congress spokesman Owei Lakemfa said the strike could go beyond Wednesday. "The strike is going on and it's quite effective across the country," he said. "We have told the police that if the arrests and harassment continue, we'll have to extend the strike."

The strike has shut down business in Lagos and other major cities but has not so far disrupted the 2.5 million barrels daily that the country exports. At least two people have been killed in clashes between police and pro-union protesters, and dozens have been arrested.

Oil giant Royal Dutch/Shell (search) said Wednesday it cut production slightly by 13,000 barrels per day after saboteurs cut through a major pipeline in the oil-rich Niger Delta (search) with a hacksaw and set it on fire.

The cutback will last a few days while repairs are made, and the damage was not expected to affect exports, Shell said.

The Labor Congress said Wednesday the government was taking it to court in an apparent bid to rule the general strike illegal. Remi Oyo, spokeswoman for Nigerian President Olusegun Obasanjo (search), would not comment.

A ruling was expected Wednesday, said Labor Congress official Joel Odigie.

Most businesses in major cities were shut down by the strike on Wednesday, though taxis were running and many private businesses were still open in the capital, Abuja.

Sporadic protests in support of the strike were seen across Nigeria, with the southern oil industry center of Port Harcourt and Lagos proving flashpoints.

Union supporters seeking to enforce the strike forcibly shut down a gas station in Lagos' Okoko district Wednesday, smashing fuel pumps and motorists' windshields.

One person was killed Tuesday in the city of Port Harcourt as police shot at stone-throwing protesters, witnesses said. In the northern city of Kaduna, a 12-year-old boy was killed Monday during clashes between police and protesters.

Crude for November delivery on the New York Mercantile Exchange (search) reached a new high of $54.45 Tuesday, after settling overnight at $53.64, fueled by continuing worries over supply in Nigeria and reduced output in the hurricane-hobbled Gulf of Mexico.