SINGAPORE, June 4 (Reuters) - Onshore fuel oil inventories in key Asia trading hub Singapore fell to more than a year's low this week as outflows firmed, data showed on Thursday.

Residual fuel stockpiles slumped 6.5% to 19.35 million barrels (about 3.05 million metric tons) in the week to June 3, Enterprise Singapore data showed. O/SING1

Total fuel oil exports from Singapore onshore tanks rose 31.1% to more than 254,000 tons in the week. The top destination was Saudi Arabia, as demand for power generation in the Middle East turned robust with the region heading into peak summer.

Saudi Arabia is expected to burn more imported fuel oil for power generation this summer, following a loss of natural gas supply from oilfields that have been shut after the Iran war curbed its oil exports, analysts told Reuters.

Meanwhile, Singapore's fuel oil imports rose 2% week-on-week to more than 680,000 tons. Indonesia and Brazil were among the top origins for the inflows.

Supplies from the Middle East remained at zero in the week to June 3, the Enterprise Singapore data showed.

Spot fuel oil premiums have been largely holding their ground this week, with backwardation remaining steep for the prompt months. FUEL/A

(Data from Enterprise Singapore)