KUALA LUMPUR, Sept. 20 (Xinhua) -- Malaysia's state-owned oil firm Petronas said Friday that its net profit grew 9 percent year-on-year to 28.9 billion ringgit (about 6.91 billion U.S. dollars) in the first half of 2019 on higher revenue.

The group said in a statement that its revenue rose 3.3 percent year-on-year to 121.1 billion ringgit in the first half ended June 30, mainly attributed to higher sales volume for petroleum products and liquefied natural gas (LNG) as well as the effect of the weakening Ringgit against the U.S. dollar exchange rate.

The increase, however, was partially offset by lower average realized prices for petroleum and petrochemical products during the period. Its profit growth was also partially offset by higher product costs.

The group's capital investments for the first half stood at 15.7 billion ringgit, attributable largely to upstream projects.

On quarterly basis, the group's revenue fell slightly to 59.1 billion ringgit in the second quarter, from 59.2 billion ringgit a year ago.

The slight reduction was mainly due to lower average realized prices for petroleum products and LNG, but it was partially offset by higher sales volume for crude oil and condensates, as well as LNG, coupled with the effect of the weakening ringgit against the U.S. dollar.

The group's net profit increased by 8 percent year-on-year to 14.7 billion ringgit, due to the effect of the weakening ringgit against the U.S. dollar, and partially offset by higher product costs.

Petronas expects global uncertainties amid trade tensions to pose challenges to the overall year-end performance.

The oil and gas market is expected to continue to be volatile in the second half amid protracted trade issues, sluggish oil demand growth as well as the slowing global economy, it said.

The group's President and Chief Executive Officer Wan Zulkiflee Wan Ariffin said the latest financial results are positive outcomes of the company's rallied commitment to constantly strive towards improvements in our operational efficiencies and commercial excellence, while maintaining fiscal discipline throughout the group.