Surging economies in China and India fed by oil and gasoline have sent prices soaring over the past year, while tensions in oil-producing nations like Nigeria and Iran have increasingly made investors nervous and invited speculators to drive prices even higher.

Violence in Nigeria helped give crude the final push over $100. Bands of armed men invaded Port Harcourt, the center of Nigeria's oil industry Tuesday, attacking two police stations and raiding the lobby of a major hotel. Word that several Mexican oil export ports were closed due to rough weather added to the gains, as did a report that OPEC may not be able to meet its share of global oil demand by 2024.

Light, sweet crude for January delivery rose $4.02 to $100 a barrel on the New York Mercantile Exchange, according to Brenda Guzman, a Nymex spokeswoman, before slipping back to $99.15.

Crude prices, which have flirted with $100 for months, have risen in recent days on supply concerns exacerbated by Turkish attacks on Kurdish rebels in northern Iraq and falling domestic inventories. However, post-holiday trading volumes were about 50 percent of normal Wednesday, meaning the price move was likely exaggerated by speculative buying.