Brent futures dropped $4.74, or 4.4%, to $102.16 a barrel by 0445 GMT after tumbling by more than $6 to $100.05 earlier in the session.
U.S. West Texas Intermediate (WTI) crude fell below $100 level for the first time since March 1, dropping $4.58, or 4.2%, to $98.43 a barrel. It fell to as low as $96.70 earlier in the session.
Both benchmarks declined by more than 5% the previous day, with Brent sliding 5.1% and WTI skidding 5.8%.