Oil prices rose on Tuesday as a cold front shut wells and refineries in Texas, the biggest crude producing state in the United States, the world’s biggest oil producer.

Prices also gained as Yemen’s Iran-aligned Houthi group said it struck airports in Saudi Arabia with drones, raising supply concerns in the world’s biggest oil exporter, and on optimism for a global economic recovery amid accelerated Covid-19 vaccine rollouts.

Brent crude was up 35 cents, or 0.6%, at $63.65 a barrel at 0434 GMT, after rising to its highest since January 2020 in the previous session.

US West Texas Intermediate (WTI) crude futures gained 82 cents, or 1.4%, to $60.29 a barrel. WTI did not settle on Monday because of a US federal holiday. Prices will settle at the close of trading on Tuesday.

“The unexpected US supply disruption provides another short term price recovery bridge that has likely taken oil prices to a level where markets were eventually heading but just a little bit quicker than expected,” Stephen Innes, chief global markets strategist at Axi said in a note on Tuesday.