Malaysian state energy firm Petronas said Wednesday its third-quarter earnings plummeted 91 percent as weak global oil prices continued to weigh on the company.

Net (LSE: 0LN0.L - news) profit at Malaysia's only Fortune 500 company for the July-September quarter fell to 1.4 billion ringgit ($320 million).

"Petronas anticipates continued challenges due to the bearish market sentiments, and will continue to focus on internal measures of control to steer the company through the downturn," it said in a statement.

Earnings for the company have taken a pounding over the past year as global oil prices have tumbled.

It (Other OTC: ITGL - news) posted a $2.02 billion loss in the fourth quarter of 2014 -- its first loss since launching quarterly earnings reports five years before -- and net profit was sharply lower in the first two quarters of this year.

Petronas is the single largest source of Malaysian government revenue and national export earnings, and its declining fortunes will add to concerns over the economic prospects of a country heavily dependent on oil exports.

Economic growth is slowing and the ringgit currency is one of the worst performing in Asia this year due in part to concerns over the economic outlook.