BEIJING, Sept 12 - China's crude oil processing rose a firm 5 percent in August from a year earlier, official data showed on Friday, as plants churned out supplies during the Olympics, and crude prices declined from record levels.

The world's number-two consumer refined 29.19 million tonnes of oil last month, or 6.87 million barrels per day (bpd), data from the National Bureau of Statistics showed.

This came on top of another overseas buying spree for oil products and record diesel imports in June and July, meaning much of August's output may have been funnelled into storage tanks and could undercut processing rates later in the year.

A near 20 percent hike in pump prices in June -- the first rise in 8 months and the biggest one-off hike ever -- has encouraged the country's oil majors Sinopec <0386.HK> and PetroChina <0857.HK> to raise run rates.

In July China's refineries had also processed 7.13 million barrels per day, as runs grew at the fastest rate in five months.

The Olympic Games opened in Beijing on Aug 8, and both the government and ordinary Chinese citizens were keen that the city, and the country, be at their best to receive dozens of heads of state, and thousands of athletes, media and tourists.

Crude runs in the first eight months gained 5.7 percent from the same period of 2007, to 229.58 million tonnes, the same daily rate as in August alone, 6.87 million bpd.

China, which produces roughly half the crude it consumes, pumped 16.03 million tonnes of oil from domestic fields last month, up 1.6 percent from a year earlier, slackening after July's surprisingly fast 5 percent growth.

The country's leaders are keen to limit dependence on costly imports and have been encouraging its firms to poor money into exploration and more efficient production.

For the Jan-Aug period, crude output climbed 2.1 percent to 126.43 million tonnes.