KUALA LUMPUR, July 8 (Reuters) - Malaysian state energy firm Petroliam Nasional Berhad (Petronas) on Monday said it would add three energy-efficient liquefied natural gas (LNG) vessels to its North American operations.

The addition of the vessels, which brings the total number in Petronas' fleet in North America to six, comes ahead of the start-up of LNG Canada's gas-export facility due later this year, the company said in a statement.

Petronas has a 25% stake in the LNG Canada plant in Kitimat, British Columbia, on the west coast of Canada.

"With the arrival of these new vessels, Petronas reinforces its commitment to deliver this much needed fuel of choice to its customers in a cost-efficient and reliable manner," it said.

The vessels were built at the Hyundai Heavy Industries (HHI) shipyard in Ulsan, South Korea. Each has a cargo capacity of 174,000 cubic meters and are the largest ships in Petronas' fleet, the firm said.

(Reporting by Rozanna Latiff; Editing by John Mair)