Oil prices surged more than 4% on Thursday after the United States imposed sweeping sanctions on Russia’s top oil producers, Rosneft and Lukoil, intensifying pressure on Moscow over the war in Ukraine.

Brent crude rose 4.3% to $65.30 a barrel, while WTI climbed 4.4% to $61.06.

The new sanctions, announced by the U.S. Treasury Department, freeze all American assets of the two companies and ban U.S. entities from doing business with them. Washington also warned of secondary sanctions for foreign banks that continue to deal with the firms.

Analysts said the move marks the toughest U.S. energy sanctions since the Trump administration returned to power. India, a major buyer of Russian crude, is already reviewing its import deals.

While prices jumped on fears of tighter supply, UBS warned that oversupply in other markets could limit sustained gains.