Huge explosions from Russian attacks on oil and gas installations lit up the night sky in Ukraine early on Sunday, while Western allies tightened sanctions to banish major Russian banks from the main global payments system.
Ukrainian forces were holding off Russian troops advancing on the capital Kyiv, President Volodymyr Zelenskiy said as the biggest assault on a European state since World War Two entered a fourth day.
But the night was brutal, with shelling of civilian infrastructure and targets including ambulances, Zelenskiy said.
Heavy fighting took place for Ukraine's second city, Kharkiv, in the northeast, where Russian troops blew up a natural gas pipeline, a Ukrainian state agency said.
That blast sent a cloud up into the darkness, though Ukraine's gas pipeline operator said the transit of Russian gas to Europe via Ukraine was going on as normal.
Kremlin-controlled energy giant Gazprom also said that Russian gas exports via Ukraine to Europe continued normally.
The United States and its allies have authorized more weapons transfers to help Ukraine fight and imposed a range of sanctions on Russia in response to the assault, which threatens to upend Europe's post-Cold War order.
On Saturday, they moved to block certain Russian banks' access to the SWIFT international payment system, making it harder for Russia to trade and for its companies to do business.
They also said they would impose restrictions on Russia's central bank to limit its ability to support the ruble and finance Putin's war effort.
"We will hold Russia to account and collectively ensure that this war is a strategic failure for Putin," the leaders of the European Commission, France, Germany, Italy, Britain, Canada and the United States wrote.
They did not name the banks that would be expelled. An EU diplomat said some 70% of the Russian banking market would be affected.
The allies initially shied away from targeting SWIFT transfers - a move the French finance minister had called a "financial nuclear weapon" - largely because of concern about the impact on their economies.
Sanctions on Russia's central bank could limit Putin's use of his more than $630 billion in international reserves, widely seen as insulating Russia from some economic harm.
Also, Google barred Russia's state-owned media outlet RT and other channels from receiving money for ads on their websites, apps and YouTube videos, similar to a move by Facebook.
