The impact of Donald Trump's wide-ranging tariffs leaked from stock markets into the commodities sector.
Oil prices dropped sharply at the start of the week after Saudi Arabia cut the cost of its flagship crude for Asian buyers by the most in more than two years.
The move, combined with fears over slowing global growth triggered by escalating trade tensions, pushed Brent crude down nearly 4% to $63.21 a barrel - its lowest level in four years. US benchmark West Texas Intermediate also fell, trading at $59.79.
Saudi Aramco reduced the price of its Arab Light crude by $2.30 a barrel for May deliveries to Asia. The decision followed a surprise announcement by the OPEC+ group to ramp up output beyond expectations.
Markets have been rocked by President Trump’s sweeping levies on global trade, prompting China, the world’s biggest oil importer, to retaliate.
Analysts say the combination of weaker demand and rising supply has revived concerns of a global oil surplus and recession.