Oil prices climbed on Monday as tensions between Russia and the West escalated, adding to supply concerns that have maintained crude prices above $100 per barrel.

By 1300 GMT, Brent oil futures had risen $1.23, or 1.3 percent, to $94.77 per barrel. West Texas Intermediate (WTI) oil futures in the United States increased $1.13, or 1.2 percent, to $92.20 per barrel.

On Monday, Russian authorities murdered a group of five saboteurs who crossed the country’s southwest border from Ukraine, according to press reports, an assertion that Ukraine dismissed as false.

French President Emmanuel Macron said earlier on Monday that U.S. President Joe Biden and Russian President Vladimir Putin have agreed in principle to a summit over Ukraine, but the Kremlin said there were no immediate plans for a meeting. read more

U.S. markets will be closed on Monday for the Presidents Day holiday.

“Energy could be clear collateral damage of a kinetic conflict between Russia and Ukraine,” said Helima Croft, global head of commodity strategy at RBC.

European Commission President Ursula von der Leyen said Russia would be cut off from international financial markets and denied access to major exports needed to modernise its economy if it invaded Ukraine.

Meanwhile, ministers of Arab oil-producing countries said on Sunday that OPEC+ should stick to its current agreement to add 400,000 barrels per day (bpd) of oil output each month, rejecting calls to pump more to ease pressure on prices.

Price gains have been limited by the possibility of more than 1 million bpd of Iranian crude returning to the market.

Iranian foreign ministry spokesperson Saeed Khatibzadeh said “significant progress” had been made in talks to revive Iran’s 2015 nuclear agreement on Monday after a senior European Union official said on Friday that a deal was “very, very close”.

Analysts said the market remained tight and any addition of oil would help, but prices would remain volatile in the near term because Iranian crude was unlikely to return until later this year.

“If a Russian invasion takes place, as the U.S. and UK have warned in recent days, Brent futures could spike above $100/bbl, even if an Iranian deal is reached,” Commonwealth Bank analyst Vivek Dhar said in a note.