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.
Output from the Organization of the Petroleum Exporting Countries (OPEC) in July reached its highest monthly level in recent history, according to a Reuters survey on Friday. This has raised concerns of oversupply with the news agency also reporting Monday that Saudi Arabia is expected to raise its prices for its light crude by around $1 a barrel – a move that is likely to hurt demand.
Meanwhile, U.S. shale rigs also continue to see a slight rebound with Baker Hughes data on Friday showing a higher rig count for a second week in a row. Sentiment has also taken a hit, with net long positions on WTI declining last week, according to the U.S. Commodity Futures Trading Commission.
Elsewhere, a worse-than-expected Chinese economic indicator on Monday did little to lighten the mood with increased concerns that demand is set to weaken in the world's second largest economy.
Nonetheless, Mahesh stressed to CNBC that sentiment would change in the near future.
"Come the next six to nine months, do not assume that OPEC will produce at these high levels," he said, citing potential disruption in Iraq.
He added that demand is also "very much underestimated" and said that U.S. shale production was still around 60 percent lower than it had been at the end of last year.
"We're expecting global oil demand to grow by close to 2 million barrels per day this year," he added.