KUALA LUMPUR, MALAYSIA - Malaysia's biggest company, state energy firm Petronas, Thursday said net profit for the fiscal year ended March 31 sank 13.9 percent year on year because of higher costs and lower crude oil prices.

"The financial year ended 31 March 2009 was a difficult and highly challenging year for the Petronas Group as the global oil and gas industry was thrust into an environment of heightened volatility and uncertainty amidst the worst global economic crisis in more than 70 years," it said in a statement.

Malaysia's biggest company in terms of profit, assets and revenue, Petronas said net profit was 52.5 billion ringgit ($21 billion) compared with a record profit of 61 billion ringgit a year earlier.

Revenue rose 18 percent to 264.2 billion ringgit - a record high for the company - due to bigger sales volumes and a stronger US dollar against the ringgit, it said.

Petronas had posted revenue of 223.1 billion ringgit in fiscal 2008.

The firm is Malaysia's only Fortune 500 company and is also among Malaysia's largest bond issuers.