LONDON (Reuters) – Oil resumed its march towards record highs, climbing above $77 a barrel on Thursday after a surprise drop in gasoline stocks in the United States and heightened supply concerns in Africa.

London Brent crude was up 62 cents at $77.38 by 0846 GMT after climbing $1.23 a day ago. On Monday it was pushed within 25 cents of last August’s $78.65 all-time high by speculative buying and a tight North Sea crude oil market.

U.S. crude, which has risen more than $7 over the past three weeks, was up 53 cents at $75.58 a barrel after a $1.03 jump on Wednesday.

Prices leapt on Wednesday after U.S. data showed refineries running harder, but failing to build up stocks of gasoline and heating oil.

Robust consumption and slower imports drained gasoline inventories by 2.3 million barrels in the week ending July 13, versus expectations of a 900,000-barrel rise.

“The data showed surprising declines and we now have to prepare for more upside. There is good potential for Brent to test its record $78.65,” said Sano Keiichi at Tokyo-based Sumitomo Corp.

Adding further support, yet more oil supply has been disrupted in Africa’s OPEC members.

Technical problems have shut in half of the 220,000 barrels per day (bpd) Dalia oilfield in Angola, operated by France’s Total.

Production in Nigeria is down by nearly a fifth, or 547,000 bpd, because of disruptions by militant groups.

In spite of the disruptions, the Organization of the Petroleum Exporting Countries has show no sign of relaxing its supply curbs and has noted crude inventories are still sharply above average levels.

Adding fuel to the price run-up, China’s economy continued to gallop ahead, with annual GDP growth accelerating to 11.9 percent in the second quarter, a faster-than-expected pace in the world’s second-largest oil consumer.

China’s crude oil imports in the first half of the year were up 11.2 percent from a year ago at 3.29 million bpd.