Western allies have announced sweeping new sanctions against Russia, including banishing its key banks from the main global payments system, as Ukraine's forces attempt to repel Russian troops advancing on Kyiv.
Russian forces pounded several cities with missiles overnight, setting an oil terminal ablaze in the town of Vasylkiv, southwest of the capital, Kyiv, its mayor said.
The blasts sent flames and smoke into the night sky, online posts showed.
"The enemy wants to destroy everything," said the mayor, Natalia Balasinovich.
The Ukrainian president's office also said Russian forces blew up a gas pipeline in Kharkiv, the country's second-largest city.
Residents there were advised to cover their windows with damp cloth or gauze and drink plenty of fluids.
Russian President Vladimir Putin launched what he called a special military operation on Thursday, ignoring weeks of Western warnings and saying the "neo-Nazis" ruling Ukraine threatened Russia's security - a charge Kyiv and Western governments say is baseless propaganda.
Reuters witnesses in Kyiv reported occasional blasts and gunfire in the city late on Saturday but it was not clear where it was coming from.
"We have withstood and are successfully repelling enemy attacks. The fighting goes on," Ukrainian President Volodymyr Zelenskiy said in a video message from the streets of Kyiv posted on his social media.
A US defence official said Ukraine's forces were putting up "very determined resistance" to the three-pronged Russian advance that has sent hundreds of thousands of Ukrainians fleeing westwards, clogging major highways and railway lines.
The US and its European partners also said on Saturday they would impose restrictions on Russia's central bank to limit its ability to support the rouble and finance his war effort.
"We are resolved to continue imposing costs on Russia that will further isolate Russia from the international financial system and our economies," said a joint statement from the United States, France, Germany, Canada, Italy, Britain and the European Commission.
After initially shying away from such a move, the allies said they were committed to "ensuring that selected Russian banks are removed from the SWIFT messaging system".
They did not name the banks that would be expelled, but an EU diplomat said some 70 per cent of the Russian banking market would be affected.
SWIFT said on Saturday it was preparing to implement the new measures in coming days.
"We are engaging with European authorities to understand the details of the entities that will be subject to the new measures and we are preparing to comply upon legal instruction," it said in a statement.
The decision - which the French finance minister had earlier called a "financial nuclear weapon" because of the damage it would inflict on the Russian economy - deals a blow to Russia's trade and makes it harder for its companies to do business.
Sanctions on Russia's central bank could limit Putin's use of his more than $US630 billion ($A871 billion) in international reserves, widely seen as insulating Russia from some economic harm.
The new measures will prevent Russia from "using its war chest", said Ursula von der Leyen, president of the European Commission, the European Union's executive.
But because Russia's large banks are deeply integrated into the global financial system, such sanctions could have a spillover effect, hurting trading partners in Europe and elsewhere.
Ukrainian Prime Minister Denys Shmygal praised the sanctions in a Twitter post on Sunday.
"Thanks to our friends ... for the commitment to remove several Russian banks from SWIFT," he posted.
The Kremlin said its troops were advancing again "in all directions" after Putin ordered a pause on Friday. Ukraine's government said there had been no pause.
A Ukrainian presidential adviser said about 3500 Russian soldiers had been killed or wounded. Western officials have also said intelligence showed Russia suffering higher casualties than expected and its advance was slowing.
Russia has not released casualty figures, and it was impossible to verify tolls or the precise picture on the ground.
The US official said Russia's forces had not made the progress that they wanted to, particularly in the north.
At least 198 Ukrainians, including three children, have been killed and 1115 people wounded so far, Interfax quoted Ukraine's Health Ministry as saying.
With additional reporting by AP