China increased net imports of crude oil by 1.4 percent in December from a month earlier as refineries maintained high operating rates to ease a diesel shortage, Bloomberg reported on Monday, citing data from the General Administration of Customs.

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China bought 20.86 million metric tons, or 4.9 million barrels a day, more than it exported last month. Overseas purchases for 2010 rose 17.5 percent from a year earlier to a record 239.3 million tons, according to the data.

China's refiners, including PetroChina Co and China Petroleum & Chemical Corp, also known as Sinopec, boosted daily oil processing to a record in November to help alleviate a shortage of the transport fuel that left at least 2,000 gas stations without supplies.

China paid an average $83.13 for each barrel it bought overseas in December, up from $78.68 in November, the data showed. The average cost of China's purchases in 2010 surged 29 percent from a year earlier to $77.05 a barrel.