Sept. 11 (Bloomberg) -- The same Mexican rebel group that carried out bomb attacks against the state oil monopoly in July claimed responsibility for pipeline explosions yesterday in the state of Veracruz.

The Popular Revolutionary Army, or EPR, said it placed 12 explosive charges along gas ducts operated by government oil company Petroleos Mexicanos, according to a statement posted to a Web site that tracks rebel groups.

The coordinated attacks against the country's energy infrastructure show an evolution of the group's ability to threaten the nation's economy. The EPR has evolved from a guerrilla group that operated only within two poor southern states in the 1990s to systematically attacking the network of pipelines that feed the country's largest companies.

``For some reason this group has shown more capacity to carry out serious attacks in the last year than it has shown in its whole history,'' said Jorge Chabat, a political science professor at the Center for Economic Research and Teaching, a Mexico City-based research group.

In today's statement the group reiterated a demand that the government release two of its members. Mexico's interior ministry has said it has no record of such prisoners in the federal system.

In its statement the group also referred to President Felipe Calderon's government as ``illegitimate'' and ``fascist.''

In a July 10 communique the EPR blamed Oaxaca governor Ulises Ruiz as responsible for holding its members captive.

On Aug. 2, when the EPR took responsibility for a bomb that damaged the front entrance of a Sears store in the city of Oaxaca, it issued a statement criticizing Calderon's preferential treatment of those on Forbes magazine's list of the world's wealthiest people. Carlos Slim, the world's richest man, owns the Sears chain in Mexico.

The group first appeared in the southern states of Oaxaca and Guerrero two years after the 1994 uprising of the Zapatista Army for National Liberation in the state of Chiapas.

In 1996, as many as 80 members of the Marxist EPR attacked government offices in the Oaxaca beach resort of Huatulco, killing about 10 people. The attacks prompted then President Ernesto Zedillo to increase patrols and boost spending on military units trained to fight insurgency groups.

To contact the reporter on this story: William Freebairn in Mexico City wfreebairn@bloomberg.net; Patrick Harrington in Mexico City at pharrington8@bloomberg.net

Last Updated: September 11, 2007 19:48 EDT