Stockpiles stand at a record three billion, the IEA said in its monthly report.
The report has added to falls on European stock markets, with the FTSE 100 shedding close to 1% on Friday.
Frankfurt and Paris also declined following sharp falls in Asian stock markets, with Hong Kong sliding 2.2%.
Investors also reacted to disappointing eurozone growth figures and a slump in commodity prices on the back of weaker demand from China. Other factors affecting confidence include fears that the Federal Reserve will raise interest rates next month and poor corporate results from heavyweights including Rolls-Royce and E.On this week. - bbc news