SAN CRISTOBAL DE LAS CASAS, Chiapas - Close to 15,000 Mayans from dozens of communities across Chiapas state took to the streets of this mountain city Friday, protesting President Vicente Fox's development plan for southern Mexico and Central America.

Known as the Puebla-Panama Plan, the initiative envisions an infrastructure, investment and tourism corridor stretching from the central Mexico state of Puebla to Panama. It aims to curb the flow of migrants from Central America and Mexico's southern states who have flooded the northern border's cities while attempting to illegally enter the United States.

But critics say the plan forces development on a region that doesn't want it and argue that Puebla-Panama will introduce technologies with which thousands of subsistence farmers across poor rural Mexico and Central America won't be able to compete.

"Today we are feeling threatened and we are here to announce that the Puebla-Panama Plan has put us on alert," said Roman Catholic Bishop Felipe Arizmendi, who led what was easily the largest street-protest of the year in Mexico's southernmost state.

Carrying hundreds of signs that claimed Puebla-Panama marginalized their interests, thousands of Tzeltal, Tzotzil and Tojolabal Mayans chanted and sang in Spanish and their native languages, snarling traffic in Chiapas' largest city for most of the day.

Arismendi said he led the demonstration "to ask God to free the Indians from the dangerous and tragic development plans that the government has in store for the region."

"The plan can only benefit business owners and foreigners and not those who really live in this region," he said.

Reached by telephone in Mexico City, some 460 miles (735 kilometers) to the northwest, a Fox spokesman said the president's office wasn't aware of the march and could not comment on it.

In June, Fox and Central American leaders ended a two-day regional summit by approving a 3 billion-dollar highway project for southern Mexico and Central America as part of the Puebla-Panama initiative.