Tightened U.S. sanctions on Moscow have disrupted a roaring trade in discounted Russian oil to China and India, reviving demand for Middle Eastern and African crudes, roiling shipping markets and driving up oil prices.

With a limited supply of sanctions-proof cargoes, discounts for Russian Urals crude to dated Brent have narrowed to $2.50-$2.90 a barrel for March delivery, versus $3-$3.50 before the January sanctions, they said, a major cost increase on a typical one million barrel cargo.