Oil prices have fallen following a cut in European growth forecasts that increased worries over the crude demand amid a global oversupply.

Brent crude for October slipped 12 cents a barrel at $50.56, while the US crude declined 20 cents at $46.55 a barrel, Reuters reported.

According to the European Central Bank (ECB), weak Chinese economy and emerging markets could push Europe into deflation soon.

"Since it will take considerably longer to reduce the oversupply than previously anticipated, we are lowering our oil price forecast."

Banks including BNP Paribas, Barclays and Commerzbank reduced their short-term price forecasts, hinting that banks expect low oil prices for a longer time.

Barclays cut its brent price forecast by $5 to $55 a barrel and to $63 a barrel for 2015 and 2016 respectively, while BNP Paribas reduced its forecasts on Thursday from $62 to $56 per barrel for 2015 and from $76 to $62 a barrel for 2016.

Commerzbank Frankfurt analysts told the news agency: "Since it will take considerably longer to reduce the oversupply than previously anticipated, we are lowering our oil price forecast."

Russia’s energy minister expects the oil market oversupply to continue in 2015.

Oil investors are keenly awaiting August jobs data in the US for indications on the health of the economy and watching for US oil rig data to get information on supply.

US policymakers will evaluate on whether to hike interest rates in 2015 based on the data.