Malaysia's Petronas warns of challenging fourth quarter amid volatile oil prices

* Q3 loss 3.4 bln rgt vs year-ago profit of 7.4 bln rgt

* Revenue drops 25%

* Volatile oil prices, weak demand to hurt full-year results

* Pengerang project on track for commercial ops

KUALA LUMPUR, Nov 27 (Reuters) - Malaysian state-owned energy giant Petronas swung to a third-quarter loss on Friday and warned the remainder of the year would remain tough due to prolonged low oil prices and demand hampered by coronavirus restrictions.

The world's fourth-biggest LNG exporter reported a loss of 3.4 billion ringgit ($836 million) for the July to September period, against a profit of 7.4 billion ringgit in the same quarter last year.

"Amid the fluid operating environment brought about by the pandemic as well as prolonged volatility of oil prices, Petronas is adopting a cautious outlook and anticipates that the remainder of 2020 will be challenging," Tengku Muhammad Taufik, president and group chief executive officer said in a statement.

"We expect our performance to be continuously affected by the volatility of oil prices aggravated by the ongoing COVID-19 pandemic," he added.

Petronas, or Petroliam Nasional Berhad, said it would continue to uphold "disciplined capital and operational spending" and preserve liquidity to ensure business sustainability.

The firm's second straight quarterly loss was attributed to a higher impairment charge on assets and higher tax expenses due to de-recognition of deferred tax assets and a lower oil and gas price outlook.

Excluding the impairment loss, Petronas recorded a profit of 2.6 billion ringgit on revenue which fell 25% to 41.1 billion ringgit.

The company said it was on track for commercial operations to begin at its $27 billion Pengerang Integrated Complex in the southern Malaysian state of Johor.

A restart of the refinery and petrochemical plants is planned for the first quarter, the firm said.

The project, in which Saudi Aramco is a partner, suffered a fire in March that killed five people. ($1 = 4.0680 ringgit)

(Reporting by Mei Mei Chu; additional reporting by A. Ananthalakshmi Editing by David Goodman and Elaine Hardcastle)