By Maryelle Demongeot

SINGAPORE 7 (Reuters) - China came close to becoming the world's second-largest crude oil importer last quarter, as North Asia's refinery maintenance season slashed Japan's imports but failed to limit galloping Chinese demand, data showed.

Heavy refinery maintenance programme in No. 2 crude importer Japan during the second quarter led to a 15 percent fall in crude imports versus the first three months.

The 640,000 barrels per day (bpd) fall in Japanese crude imports was in line with the 14 percent of refining capacity estimated to have been taken offline in the second quarter, or an average of 682,000 bpd, Reuters calculations based on official data showed.

The routine shutdowns cut total Japanese refining capacity by 7 percent and reduced imports by 5 percent from the same period a year ago.

South Korea showed a more modest 3 percent decrease in crude imports from a year ago.

In contrast, China's crude imports grew 5 percent between April and June to 3.361 million bpd, just behind Japan's average of 3,731 million bpd.

This came as Chinese refineries cut maintenance to a minimum, as refining margins were recovering.

Compared with a year ago, China's crude imports were up 16 percent, with most of the increased inflows coming from Iran and Sudan. Imports from Iran were up 40 cent, while shipments from Sudan jumped almost eightfold after the start-up of Dar Blend crude exports in late-August, 2006.

The world's second-largest oil consumer bought nearly half of Sudan's monthly output, and about two thirds of the African country's oil exports, for the third quarter in a row.

State oil firm China National Petroleum Corp. (CNPC) has a 41 percent stake in the Dar Blend field, which began pumping last year.

China's healthy oil demand led North Asian crude imports to reach 8.475 million bpd during the second quarter, down from 10.053 million bpd during the first quarter when winter demand is strong, but still up 3 percent from a year ago.

OPEC CUTS BUT LESS

Top oil exporter Saudi Arabia shipped out 8 percent less crude on average than a year ago to its three key Asian buyers, as it continued to stand by its OPEC pledge to curb exports.

Saudi exports to the three North Asian countries that together absorb about a third of the oil kingdom's oil, was at 2.250 million bpd during the second quarter, down about 31,000 bpd from the first and 188,000 bpd lower than a year ago.

Saudi Arabia pledged to cut 380,000 bpd from Nov. 1, 2006, and later to 538,000 bpd from Feb. 1.

Total Iranian crude imports into North Asia were up one quarter from a year ago.