More problems on the oil supply front.

In an apparent case of politically motivated sabotage, six explosions blew apart oil and natural gas pipelines operated by Mexico's Pemex state oil and gas monopoly early Monday in Veracruz and Tlaxcala states, causing fires and forcing the evacuation of 15,000 people from surrounding towns.

The blasts forced Pemex to shut down at least four affected pipelines and prompted federal authorities to close two major roads. No injuries were reported.

Mexico is the world's sixth-largest oil producer and a major supplier of petroleum to the U.S. The outages drove the price of oil above $78 a barrel in futures trading Monday.