Mexico City  - Dawn's light found leftist legislators occupying the two chambers of the Mexican Congress Friday in a "civil resistance" move against proposed reform of the country's energy sector.

The legislators spent the night in sleeping-bags in the chambers.

In the early hours of Friday, legislators of the three parties that make up the Broad Progressive Front (FAP) of former presidential candidate Andres Manuel Lopez Obrador waved Mexican flags and placards against the "privatization" of the state oil company Petroleos Mexicanos (Pemex).

On Tuesday, President Felipe Calderon proposed sweeping reforms of Pemex, including the creation of "citizens' bonds" to raise fresh money for the company and provide dividends to private investors.

In a nationwide address, Calderon outlined six major measures to reform the company but insisted that Pemex "is not being privatized." He said it will continue to be a state firm and that the constitution would not be changed.

The reforms envision financial and administrative autonomy with greater facility to contract out major capital projects, including the construction of new refineries, he said.

Mexico currently imports four out of every 10 litres of gasoline consumed in the country.

The ruling National Action Party (PAN) and the Revolutionary Institutional Party (PRI) have rejected the protests. Together, they have enough votes to push through the reform despite the opposition of the FAP.

Leftist legislators - who already occupied Congress twice in 2006 - have threatened to remain in the building indefinitely.

The proposed reform would not alter the Mexican constitution, which gives Pemex a monopoly of fundamental areas linked to the exploitation of oil: exploration, extraction, refining, commercialization, petrochemicals, among others).

However, it does open up some of those areas for private initiative, through secondary legislation.(dpa)