At least five people were injured in clashes between several hundred protesters and police outside the auction venue in Rio de Janeiro Monday. Police used tear gas and rubber bullets when trade unionists, students and left-wing party representatives attempted to get past security at the hotel in Barra da Tijuca. The protesters responded by throwing stones and setting up a barricade using a vehicle belonging to the Record TV network.

At the auction, the four energy companies won 35-year concessions to develop the so called "pre-salt" oil deposits in the Libra field below a layer of salt in the Atlantic Ocean, which is estimated to hold 12 billion barrels of oil.

The foreign companies and Petrobras were the only consortium to offer the Brazilian government the minimum of 41.65 percent of the oil to be extracted from the site. It's the first oil auction held under the new rules which give more power to Petrobras.

Petrobras took a 40 percent stake, Shell and Total secured 20 percent, and 10 percent went to CNOOC and CNPC each.

The pre-salt deposits span 149,000 square kilometers (58,000 square miles) and Libra is located 183 kilometers (80 miles) off the coast. Brazil currently produces 2 million barrels of oil a day, but is looking to more than double that number to 4.3 million per day by 2020, in large part due to the pre-salt deposits.

dr/mkg (AP, AFP, dpa)