In pictures: Mexico's Pemex protests

Mexican police try to control a crowd during a march to protest against reform of Pemex, Monday, 1 July

Mexican President Enrique Pena Nieto's promise to overhaul state-owned oil firm Pemex has sparked angry protests in the capital, Mexico City.

A demonstrator wears a helmet with a sticker that reads "Pemex is not for sale" during a protest against the privatisation of the state oil monopoly Pemex in Mexico City, 1 July

The demonstrators suspect the government is planning to privatise Pemex, which has long been a symbol of national pride for many Mexicans. The slogan "Pemex is not for sale" was emblazoned on hats and scrawled on walls during the march.

A demonstrator writes graffiti, which reads "Pemex is not for sale", during a protest against the privatisation of the state oil monopoly Pemex in Mexico City, 1 July

The government says it wants to allow Pemex to raise more private capital to pay for much-needed infrastructure development and further exploration of Mexico's undersea reserves.

A masked demonstrator holds up a Mexican flag during a march to protest against an alleged government plan to privatize Pemex, 1 July

Some of the protesters donned the V for Vendetta mask that has become the ubiquitous symbol of protests from Turkey to Brazil.

Police officers stand guard at the Angel of Independence monument before a protest against the privatisation of the state oil monopoly Pemex in Mexico City, 1 July

Police were out in force to protect the city's landmarks, but the rally passed off peacefully.

A demonstrator holds a Mexican national flag in front of riot policemen during a protest against the privatisation of the state oil monopoly Pemex at the Angel of Independence in Mexico City, 1 July

The issue remains one of the clearest dividing lines between Mr Pena Nieto and his left-wing opponents, and could be a deciding factor in local elections due this weekend.