Gold prices rose on Tuesday after Moderna's chief warned that COVID-19 vaccines are unlikely to be as effective against the Omicron variant as they have been against the Delta version.

Spot gold rose 0.3% to $1,790.92 per ounce by 0728 GMT.

US gold futures increased 0.4% to $1,792.90.

The Moderna chief's comments rattled financial markets, with Asian shares dropping to their lowest in more than a month while crude oil futures fell over 2%.

"It is hard to say how much of an impact this will ultimately have on gold as markets are still digesting the comments," CMC Markets UK's chief market analyst Michael Hewson said, adding bullion prices could head back to the $1,800 level if equity markets decline further.

Investors will pay close attention to US Federal Reserve Chairman Jerome Powell's congressional testimony later this week after he warned on Monday that the new COVID-19 strain muddied the central bank's inflation outlook and prices could continue to rise for longer than earlier thought.

"Powell has the tendency to talk markets into a state of calm and he might hint that the Fed is prepared to slow down the pace of stimulus withdrawal, providing some support to gold," DailyFX currency strategist Ilya Spivak said.

"But any rally in gold is unlikely to be sustained as we still don't know how receptive this variant will be to vaccines. So far, we have one comment from one person, albeit an important one, and the Fed needs more clarity before it commits to slowing the pace of tapering."

Reduced stimulus and interest rate hikes tend to push government bond yields up, raising the opportunity cost of gold, which pays no interest.

Spot silver fell 0.2% to $22.84 per ounce. Platinum dropped 1.4% to $949.55 and palladium gained 0.1% to $1,795.91.