Most stock markets rose on Monday as oil prices tumbled after United States President, Donald Trump announced an energy ceasefire between Russia and Ukraine, offsetting a fresh wave of Houthi attacks on Saudi Arabia.

Both main crude contracts sank more than one percent following the US president’s declaration, even as it sparked astonishment in Kyiv, which also said Moscow had struck multiple power plants in the country.

Brent crude was down 1.2 percent at 103.48 dollars per barrel on Monday morning.

Trump announced the ceasefire early Sunday on Truth Social, writing, “Effective immediately, there is an ENERGY CEASEFIRE in the War between Russia and Ukraine. Both parties have agreed. Do not break it!”

His post came after he called on Ukrainian President Volodymyr Zelensky to halt attacks on Russian refineries and said it was time for Ukraine to get a new president who would finally settle the war.

Zelensky appeared to express surprise at the announcement, saying he was seeking further details, but added that Ukraine supports the ceasefire, and it is important that Russia support it as well. Russia has yet to confirm its agreement.

The announcement triggered mixed reactions across global markets. In New York, the Dow Jones and S&P 500 opened higher as investors welcomed the prospect of reduced pressure on energy infrastructure.

European markets also recorded gains, with energy intensive industries leading the rally on hopes that lower oil prices would ease production costs.

The drop in oil prices reversed an initial spike that came in response to Houthi attacks on Saudi Arabia at the weekend. At least a dozen people were killed at Riyadh’s international airport on Saturday in the deadliest attack on Saudi soil for more than a decade, with another death reported after a second strike on Sunday.

The Iran backed group on Sunday claimed multiple attacks over the past 24 hours and threatened to keep targeting the kingdom’s transit hubs, calling them a theatre of operations for its forces. The assaults marked a sharp escalation in the Yemen conflict, where Riyadh has long supported the internationally recognised government against the Houthis.

Analysts said the energy ceasefire, if it holds, could bring temporary relief to global energy markets that have been volatile since the start of the war in Ukraine. Attacks on refineries and power plants by both sides have previously caused sharp fluctuations in crude and gas prices.

While the announcement was welcomed by some of Ukraine’s allies, Trump had come under fire after declaring a temporary easing of US sanctions on Russian diesel, which European leaders and Kyiv said would only embolden Russian President Vladimir Putin.

Observers note that a durable ceasefire on energy infrastructure would be significant for both countries. Ukraine’s power grid has faced repeated strikes during winter months, while Russia’s refining capacity has been impacted by long range drone attacks. A pause could help stabilise supplies as winter approaches.