President Dilma Rousseff vetoed 12 of the 84 articles of a widely criticized land-use bill, including an amnesty for people who contributed to deforestation in Brazil's Amazon region, the government said Friday.

The head of state also blocked a provision that would reduce the size of forested buffer zones around rivers from 30 meters (100 feet) on either side to 15 meters.

The vetoes were announced at a joint press conference by the ministers of environment, Izabella Teixeira; agriculture, Jorge Mendes Ribeiro; and rural development, Gilberto Jose Vargas.

Rousseff blocked the 12 articles in the interest of conservation and sustainable agricultural production, the ministers said.

Congress can override the president's vetoes.

Domestic and international environmental groups had urged Rousseff to block the entire bill, with Greenpeace mounting a months-long campaign under the banner, "Veto It, Dilma."

Opponents of the revised Forest Code say it will open the door to more agri-business activity in areas that have already suffered serious environmental degradation, especially in Amazonia.

One of the most controversial sections of the bill would provide broad amnesty from fines to large farmers who cleared more trees than legally permitted and are currently growing crops in those degraded areas.

Environmentalists' latest attempt to lobby Rousseff took place Thursday, when the Avazz group delivered to the presidential palace a petition bearing 2 million signatures urging the president to veto the entire bill.

Around 1.7 million of the signatures came from abroad, notably France and Germany, Avazz spokesman Pedro Abramovay told reporters, stressing "the global concern" about the fate of Amazonia if the new Forest Code becomes law.

The bill has also drawn criticism from a group representing Brazil's federal judges, who said it could lead to an "avalanche of lawsuits" because of constitutional inconsistencies in the text.

Consea, a presidential council on food security, likewise urged Rousseff to veto the bill, warning the new Forest Code would have a "grave impact on the nutritional security of the Brazilian population." EFE