MEXICO CITY -- A Mexican rebel group that waged a short-lived armed struggle against the government 13 years ago issued a declaration Monday in support of a Marxist group responsible for recent attacks on the country's oil and gas pipelines.

The Zapatista National Liberation Army did not explicitly condone the Sept. 10 and July 11 attacks, which temporarily cut the delivery of gas and oil and cost businesses hundreds of millions of dollars.

But it said the demand of the so-called People's Revolutionary Army that the government release two of its imprisoned members "is not only legitimate, it is also a complaint against the dirty war being revived by that lover of military uniforms, (President) Felipe Calderon."

The statement was posted on the Zapatistas' Web site and sent to news media outlets in Mexico on Sunday. It could not be independently verified.

Calderon's office did not immediately issue a response.

The People's Revolutionary Army, or EPR, a secretive Marxist group that killed dozens of police and soldiers in the late 1990s, has claimed responsibility for two separate, multipronged attacks on pipelines operated by the state-owned oil company Petroleos Mexicanos, or Pemex.

The EPR, which has been largely inactive in recent years, also threatened to carry out additional attacks until authorities release two rebels they believe are in government custody.

The government has denied holding the men, and Attorney General Eduardo Medina has suggested that they may have fallen victim to internal divisions within the guerrilla movement.

The Zapatista National Liberation Army, known by its Spanish acronym EZLN, seized the main city of San Cristobal de las Casas and other Chiapas communities in the name of socialism and Indian rights on Jan. 1, 1994.

A cease-fire ended fighting between rebels and government forces after a few days, and the two sides have since maintained an uneasy truce.

The Zapatistas are led by Subcomandante Marcos, a ski-masked man whom the government has identified as a former professor.

Marcos, believed to still be holed up in the jungle, now advocates a quieter social revolution while issuing occasional missives harshly critical of Mexico's politicians and government policies.

In their statement Sunday, the Zapatistas emphasized their "civil and pacifist" methods, which have included the establishment of autonomous regional Indian governments.

The EPR and other revolutionary groups in Mexico "are organizations with which we have our differences in terms of formation, structure, method, analysis and history, but which we recognize and respect," the statement said.

The Zapatistas added that they would cancel a planned upcoming visit to Mexico's southern and central states -- not because of any threats from the EPR but because "the military government of Felipe Calderon could mount an attack and later try to blame it on the EPR."