VERACRUZ, Mexico — A leftist guerrilla group took credit for a string of explosions that ripped apart at least six Mexican oil and gas pipelines Monday, rattling financial markets and causing hundreds of millions of dollars in lost production.

The explosions could be seen for miles, and set off fires that sent flames and black smoke shooting high above Veracruz.

At least a dozen pipelines, most carrying natural gas, were affected, said Jesus Reyes Heroles, the head of Mexico's oil monopoly Petroleos Mexicanos.

The blasts caused brief jitters in international markets, with natural gas futures up as much as 20.2 cents on news of the explosions, although prices dropped in later trading. One oil pipeline was hit in Monday's attack but Pemex said the damage wouldn't affect crude exports.

Some local factories were forced to shut down after natural gas supplies were cut. Residential supplies were not expected to be affected.

There were no immediate reports of injuries directly caused by the explosions.

By The Associated Press