Traders have booked at least 10 million barrels of Russian Urals, Kazakhstan's CPC Blend and North Sea crude to load in August for China and South Korea, while also eyeing West Africa and Libya supplies for Asia, said several sources with knowledge of the deals, including two involved in some of the trades.

The arbitrage purchases come as buyers seek oil to replace more expensive supplies from the Middle East and as Iranian exports to Asia fall ahead of U.S. sanctions.

European crude exports to Asia last peaked for loadings in May at 34 million barrels, trade flows data on Eikon showed.

"The arb (arbitrage) is open," said one of the sources, who buys crude for a North Asian refiner and has been making inquiries on the shipments.

"Light crude supply is abundant. There are so many cargoes available so we have to look at their economics," he said. There are also U.S. grades to choose from, he said.

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or graphic on Europe crude loadings to Asia click

Asian buyers are turning to the Atlantic Basin for oil supplies at the expense of the Middle East after Brent's premium to Dubai swaps fell below $2 a barrel on Thursday.

The spread between the two benchmarks is at its narrowest since October, making Dubai-linked grades more expensive than those from Europe and Africa. Middle East and some Russian grades - ESPO, Sokol and Sakhalin Blend, exported from the Pacific - are priced off Dubai assessments in Asia.

Unipec, the trading arm of Asia's largest refiner Sinopec, has bought about 4 million barrels for loading in August, made up mostly of Russian Urals and some North Sea crudes, sources said.

China, the world's top crude oil importer, last imported 2 million barrels of Russian Urals in June, according to trade flows data on Thomson Reuters Eikon.

South Korean refiner Hyundai Oilbank has bought about 2 million barrels of North Sea Forties crude to be delivered in late October, four months after its previous import in June, the sources also said.

Unipec declined to comment. Hyundai Oilbank said it does not comment on its trades.

South Korea is also keeping imports of CPC Blend from Kazakhstan elevated, loading 5 million to 6 million barrels in August, the sources said.

South Korea, the fifth-largest global oil importer, has imported 4.8 million to 6 million barrels of CPC Blend per month between March and June, to replace light grades such as Abu Dhabi's Murban, according to trade sources and Eikon data.

As Atlantic Basin supplies to Asia swell, Middle Eastern grades have come under pressure with September-loading cargoes trading at discounts to their respective price markers, while spot premiums for Russian Far East grades hit multi-month lows.

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r graphic on brent crude's premium to Dubai click

(Reporting by Florence Tan in SINGAPORE and Dmitry Zhdannikov in LONDON; Additional reporting by Jane Chung in SEOUL; Editing by Tom Hogue)

By Florence Tan and Dmitry Zhdannikov