Brent crude futures were down $3.15, or 3.0%, at $103.50 a barrel by 0326 GMT. They touched $103.41 earlier in the session, the lowest since April 12.
U.S. West Texas Intermediate (WTI) crude futures fell $3.01, or 3.0%, to $99.06 a barrel, having skidded earlier to $98.93, the lowest since April 12.
The benchmarks lost nearly 5% last week on demand concerns.