From Reuters, via the IHT:

Zhuhai Zhenrong Trading, a Chinese state-run company that is the biggest buyer of Iranian crude oil worldwide, began paying for its oil in euros late last year as Tehran moved to diversify its foreign exchange reserves away from U.S. dollars. The company, which buys more than a tenth of the oil exports from Iran, has changed the payment currency for the bulk of its contract of roughly 240,000 barrels per day, the people said. [Full text]