Russian forces bombed areas of the Ukrainian capital Kyiv on Wednesday and U.S. President Joe Biden arrived in Brussels for a series of summit meetings on the war while NATO's chief said the alliance was bolstering battle groups in Eastern Europe.
NATO, G7 and EU summits will on Thursday discuss the conflict, which began on Feb. 24 and has caused more than 3.6 million refugees to flee the country and already led to the unprecedented isolation of Russia's economy.
Responding to a slew of sanctions that have already frozen assets and hit individuals and firms, President Vladimir Putin said Moscow planned to switch gas sales made to "unfriendly" countries to roubles, alarming international markets.
Biden's visit could also shine light on a dispute with European allies, some of whom are heavily reliant on Russian oil and gas, over whether to impose further energy sanctions.
The issue has been a "substantial" topic and the subject of "intense back and forth" in recent days, White House national security adviser Jake Sullivan told reporters.
The U.S. plans to announce more sanctions on political figures and oligarchs, he said.
Biden will start his visit by meeting NATO Secretary-General Jens Stoltenberg, who on Wednesday said the alliance will boost its forces in Eastern Europe by deploying four new battle groups - in Bulgaria, Hungary, Romania, Slovakia. "I expect leaders will agree to strengthen NATO's posture in all domains," he said.
Moscow calls its actions in Ukraine a “special operation” that it says is not designed to occupy territory but to destroy its southern neighbour's military capabilities.
The West says this a baseless pretext for an unprovoked war.
And in a sign of disquiet at home, a veteran aide to Putin, Anatoly Chubais, resigned over the war and has left Russia with no intention to return, two sources said. He becomes the first senior official to break with the Kremlin since the incursion.
Although the Kremlin says its operation is going to plan, Russian forces have taken heavy losses, got stuck on most fronts and face supply problems. They have turned to siege tactics and bombardments, causing huge destruction and many civilian deaths.
Kyiv's mayor, Vitali Klitschko, told reporters on Wednesday that 264 civilians in the city had been killed by Russian attacks. He later said that one person was killed and two wounded on Wednesday when shells hit a shopping centre parking lot in a northern part of Kyiv.
Russia has denied targeting civilians.
Ukrainian President Volodymyr Zelenskiy on Wednesday night called on people all over the world to take to the streets on Thursday, four weeks since Russia invaded, to demand an end to the war.
"Come from your offices, your homes, your schools and universities, come in the name of peace, come with Ukrainian symbols to support Ukraine, to support freedom, to support life," he said in an English-language video address.
U.S. Secretary of State Antony Blinken said the United States has assessed that members of Russia's forces have committed war crimes in Ukraine.
