The weekly average prices of the Organization of Petroleum Exporting Countries (OPEC) dropped significantly last week, shedding more than six U.S. dollars to 109.35 U.S. dollars per barrel, the Vienna-based cartel said Monday.

Weekly OPEC price had been on the rise for four consecutive weeks before last week's downfall, but the growth rates had witness a decreasing trend over the past month.

Through the last week of July, the figure only rose by 0.1 dollars per barrel.

OPEC daily oil prices also declined from 113.57 dollars a barrel last Monday to 103.30 dollars per barrel on Friday, declining by more than nine percentage points over the week.

The U.S. economic growth prospects and the European sovereign debt crisis are among the major factors that drove down the prices.

Saudi Arabia's oil production increase as well as the International Energy Agency's decision in June to put two million barrels per day of crude oil into the market for a month also contributed to the oil price losses.

Already, the current declining trend in oil price has put OPEC member countries on alert. OPEC representative of Iran said that if the oil price continued to decline, an OPEC oil ministerial meeting would be convened to discuss countermeasures.