Oil prices fell sharply below $70 a barrel on 24 September after an unexpected increase in stocks in the US, the world’s largest consumer.

The US’ November West Texas Intermediate (WTI) contract was trading at $67.70 a barrel, down $3.40 from a week before.

Europe’s Brent contract was trading at $68.20 a barrel at the same time, down $2.95 from seven days earlier.

A report released by the US’ Energy Information Administration (EIA) on 23 September showed that stocks of crude oil in the US had grown by 2.8 million barrels during the week ended 18 September 2009, reaching a total 335.6 million barrels.

This sparked a wave of selling in open markets, pushing prices down, analysts say.

Analysts at the UK’s Barclays Capital, the investment arm of the UK bank say that the fall will be shortlived, however, and that prices will remain in a $65-75 a barrel range for the foreseeable future.

The average price of the 12 Opec members’ crude oils was $68.87 on 23 September, down $1.10 from a week before.