VIENNA, July 7 (Xinhua) -- The weekly average prices of the Organization of Petroleum Exporting Countries (OPEC) surged 6.71 dollars higher to 138.31 U.S. dollars per barrel (dpb) last week, said the Vienna-based cartel Monday.

    The daily prices steadily rose from 136.03 dpb Monday to 137.73 dpb Wednesday and surged 3 dollars higher in just one trading day, hit an all-time high of 140.73 dpb Thursday. The prices retreated slightly to 140.14 dpb Friday, remained however over 140 U.S. dollars.

    OPEC President Chakib Khelil said Sunday that the current high oil prices were mainly due to the phenomena that have nothing to do with supply and demand.

    He warned that the prices would rise again in the coming weeks, due to weak dollars, geopolitical problems and other reasons.

    Experts pointed out that the tension of the Iran problem, consecutive devaluation of the U.S. dollars were main reasons leading to high prices. OPEC oil prices have risen about 50 percent since the beginning of this year.