The new discovery at block 114, 65km (40.39 miles) off the coast of Quang Tri province, comes as the Southeast Asian country's oil and gas industry struggles to maintain its output as reserves run low, with regional tensions over the South China Sea having affected its offshore activities.

The operator of the block is assessing reserves and aims to start production there in 2028, PetroVietnam said in a statement on its website.

The block is operated by Eni Vietnam B.V. and ESSAR E&P Limited.

The discovery has helped PetroVietnam to meet its target of raising its reserves for this year, the government said in a separate statement without elaborating.

"This is important in paving the way for further exploration and production activities in the block and its adjacent area," the government said.

Vietnam's crude oil output in the first seven months of this year fell 14.1% year on year to 5.72 million tonnes, government data showed on Wednesday. Its natural gas output fell 8.8% to 5.65 billion cubic metres.

By Khanh Vu