Brent crude oil, the European benchmark, dropped on Monday to less than $100 for the first time in more than 14 months on a strong supply situation despite unrest in producer regions.
Brent hit $99.72 a barrel to record its lowest level since June 24, 2013 after coming under pressure in recent weeks also from easing demand growth expectations.
The price of Brent has fallen by more than 13 percent since June 19, when it reached a nine-month high point of $115.71 a barrel amid major unrest in key crude producer Iraq.
In midday deals, Brent North Sea crude for delivery in October had recovered to stand at $100.10 a barrel, down 72 cents compared with Friday's close.
US benchmark West Texas Intermediate for October dropped 54 cents to $92.75 a barrel.
Lower oil prices benefit companies and households while impacting revenues for producer countries, including those who together comprise the OPEC cartel.
Saxo Bank analyst Ole Hansen said Chinese data had helped to push oil prices lower on Monday.
"China's crude imports for August showed a year-on-year decline while export of fuel exceeded imports for the fourth time this year. This is adding to the current negative sentiment which continue to be driven by rising supplies at a time of slowing seasonal demand," he added.
- Slower demand growth -
Last month, OPEC trimmed its 2014 forecast for global oil demand growth after weaker-than-expected economic growth in rich countries in the second quarter and amid what it described as a fragile worldwide recovery.
A disappointing US jobs report published last Friday meanwhile tempered sentiment about demand in the world's top crude consumer.
"The unexpectedly weak US jobs number puts doubt in the US economic outlook and in turn, weakened oil demand," Singapore's United Overseas Bank said in a note to clients.
The US officially added 142,000 new jobs in August, snapping a six-month streak of more than 200,000 jobs per a month and far below the 223,000 tipped by analysts.
The data supported the view that the world's biggest economy is still struggling to pick up speed, and that wages remain very flat, holding back consumer spending.
Analysts on Monday said oil was being pushed down in part by a resumption to production in Libya despite the country's unrest.
"On the supply side Libya, despite governmental chaos, has pushed production over 700,000 barrels per day and a stronger dollar is taking its toll on the demand side," oil brokers PVM said in a note to clients on Monday.
A stronger US unit makes dollar-priced oil more expensive for buyers using weaker currencies, denting demand.
- Eyes on Ukraine -
Desmond Chua, market analyst at CMC Markets in Singapore, said markets are likely to trade sideways this week owing to a dearth of trading cues.
"We see a rather muted week of data, with markets likely to take direction from geopolitical factors like the ceasefire in Ukraine at the forefront," Chua said.
The conflict is closely watched by crude investors as Russia is the number-two oil producer in the world, and Ukraine is a key conduit for Moscow's gas exports to Europe.
Fighting around two flashpoint cities in eastern Ukraine on Sunday rattled a tenuous truce between government troops and pro-Russian rebels less than 48 hours after it came into force.
Western nations have warned of more sanctions against Moscow for its support of the pro-Kremlin insurgents in the civil war, which has cost about 2,600 lives.
Russian President Vladimir Putin has so far denied any direct involvement in the months-long conflict.