China increased its crude imports in the first quarter to fill stockpiles and not because of growth in domestic demand, according to a report in China National Petroleum Corp.'s online newsletter.

China's crude-processing capacity expanded by 3 percent in the first quarter, much slower than the annual growth rate of as much as 12 percent from 2006 to 2010, CNPC said today in the newsletter. The nation boosted oil imports amid geopolitical tension to ensure long-term energy security, it said.

"It shows that China is concerned about the instable global oil market," according to the report. "China will have more crude-storage facilities coming online later this year and early next year. Crude imports in the first quarter were probably just the tip of iceberg."

China, the world's second-biggest oil consumer, imported 70.6 million metric tons of crude in the first three months, up 11 percent from a year earlier, according to customs data. The nation’s diesel-consumption growth this year will be lower than output growth, the report also said.