State oil and gas group PetroVietnam has acquired all of the Vietnamese assets of U.S. oil major Chevron Corp as it seeks to boost gas output, the Vietnamese group said.

Under a deal signed on June 17, PetroVietnam will take over Chevron's stakes in three offshore blocks and in a natural gas pipeline project linking them to southern Vietnam, the Hanoi-based group said in a statement sent to Reuters late on Wednesday.

The acquisition of Chevron's Vietnam assets will help accelerate field development "to make gas more quickly available", PetroVietnam chairman Nguyen Xuan Son said in the statement.

The company gave no value for the acquisition.

The move followed a downward adjustment by PetroVietnam of its energy reserves for this year due to a slump of global oil prices, and the possible sale of its 40 percent stake in a joint venture in Venezuela.