Thousands of Mexicans took to the streets Sunday to vent frustration with President Enrique Pena Nieto's plans to inject foreign capital into the politically sensitive state-owned oil industry.
As many as 12,500 people answered the call of leftist opposition leader Andres Lopez Obrador to march peacefully against the plans, a public safety official said.
"They want to share out with foreign oil companies, the earnings of the people, the nation," said Lopez Obrador, charging the plan was an affront to Mexican sovereignty.
He called on supporters to reject energy industry reforms, unless they are put before the people in a referendum vote.
Lopez Obrador urged Pena Nieto to change his stand and agree to a referendum, and said there would be more marches and civil disobedience as they await a government decision.
State oil giant Pemex generates more than a third of the money that funds the government's budget.
Its output has slid from 3.4 million barrels per day in 2004 to 2.5 million in 2012.
The government wants to raise money with foreign partners for high-cost, super-deep oil exploration beneath the Gulf of Mexico.