The price of Brent crude sank below $83 a barrel on Friday as the US Dollar hit a four-year high.

Supply continues to outstrip demand in many markets, meaning benchmark Brent has now reached its lowest level in four years.

Meanwhile, the dollar reached its highest level since June 2010 against a basket of major currencies.

A stronger dollar tends to dampen demand for dollar-denominated commodities like oil.

Brent was trading at $82.56 on Friday morning, down more than 25% from a June high of $115 a barrel.

Analysts predicted that a strong showing in US employment data, due to be released on Friday afternoon, could push the dollar even higher.

Opec forecast on Thursday that its market share could shrink by 5% by 2018 as shale supplies increased at a faster rate than demand.

However, the cartel said it expected prices to recover in 2015.

"I think the price will rebound by the second half of next year. But I don't know by how much. This situation of low prices cannot continue," said Opec Secretary General Abdullah al-Badri.