Brent fell over 2 percent to $51.10 a barrel by 10:00 a.m. to a price not seen since the end of January. Reuters reported that the benchmark is now on its longest weekly losing streak since late 2014.
U.S. crude, meanwhile, fell 68 cents to $46.43 a barrel after hitting its lowest in four months at $46.35 a barrel. However, it was still off its March low which saw the commodity dip below $43 a barrel.
Barclays oil analyst Miswin Mahesh told CNBC Monday that a number of factors had coincided to inevitably lead to a price decline, but remained upbeat on the price over the longer term.
"As much as things are looking weak at the moment, I think the price in itself would be a catalyst to tighten market balances come 2016," he said.
Barclays expect Brent to rebound to $66 a barrel by the second quarter of 2016 and WTI to reach $63 a barrel.
Analysts have highlighted a raft of reasons for the latest fall with several data points weighing heavily on Monday morning.