Tens of thousands of people have marched in Mexico City to protest against constitutional reforms pushed through by President Enrique Pena Nieto to open the oil and gas industry to foreign investment.
An estimated 65,000 people gathered for the protest on Friday in the Zocalo - a main square in the capital city - an official at the Secretariat of Public Safety told the AFP news agency.
At least 2,500 police officers were deployed but there were no incidents of violence, the official said.
The march was organised by the Party of the Democratic Revolution (PRD), the leftist opposition to the president's ruling Institutional Revolutionary Party (PRI).
One of PRD's founders, Cuauhtemoc Cardenas, claimed that the foreign investors "will be interested in extracting the largest amount of petroleum possible in the shortest amount of time".
The reforms, which open Mexico's oil industry to foreign investment for the first time in 75 years, were approved in Congress and ratified by a majority of Mexican states in late 2013.
The rule changes are supported by two of the country's leading parties, the PRI and the conservative National Action Party (PAN).
In 1938, foreign oil companies were expelled by then president Lazaro Cardenas, who is Cuauhtemoc Cardenas' father.
"All types of protest are valid" in opposing the reforms, Cardenas told the crowd in the Zocalo, "including civil disobedience."
The PRD is hoping to hold a referendum in 2015 to overturn the measures.