Oil prices had risen as much as 13 per cent since the Opec announced on September 27 a production cut to support prices
Russia expects to increase its oil output by 0.7% next year and a further 0.9% in 2018
Disagreements remain over which members should be exempt from a curb to reduce output to a range of 32.5-33 mn bpd
Saudi Arabia and Gulf allies express their will to reduce peak oil output by 4% this week to Russia
Traders remain cautious of the Opec's ability to cut production come late November
The dollar, which held near nine-month highs against a basket of major currencies, also weighed on prices
Iraq wants to be exempted from Opec production cuts
Traders said the price falls followed comments from Iraq, which said it wanted to be exempt from a production cut
Oil production from OPEC nations hit a record last month, although members have agreed to come up with a plan to reduce it
Venezuela's concerns are because of collapsing oil prices
The dollar rose to its highest level since March against a basket of other leading currencies on Friday
International Brent crude oil futures were up 3 cents at $51.41 per barrel
The OPEC plans to meet on November 30 and hopes to decide on a half a million to one million barrels per day oil production cut
US West Texas Intermediate crude was up 40 cents, or 0.8 per cent, at $50.34 a barrel
A drop in the dollar away from seven-month highs the previous day also supported crude
Despite Monday's falls, analysts said that traders were cautious about driving the market much further down
A closely watched report on Friday by oil services provider Baker Hughes showed US drillers added four rigs in the week to Oct 14
Crude and gas producers to gain, with oil up 18 per cent since January
But, doubts over the feasibility of a planned production cut still weighed on markets
The US Energy Information Administration reported a drop of 3.7 million barrels for distillates late on Thursday