Fighting continues as Russian troops enter Ukraine's 2nd largest city of Kharkiv

Ukrainian authorities said on Sunday that Russian troops have entered Ukraine's second-largest city of Kharkiv and fighting is underway in the streets.

"The Russian enemy's light vehicles have broken into Kharkiv, including the city centre," said regional governor Oleh Sinegubov.

"Ukraine's armed forces are destroying the enemy. We ask civilians not to go out."

SWIFT, the global finance arm that the West can twist

Videos published by Anton Herashchenko, adviser to the interior minister, and Ukraine's State Service of Special Communications and Information Protection showed several light military vehicles moving along a street and, separately, a burning tank.

Meanwhile, Moscow claimed today that its troops have "completely blocked" the southern Ukrainian cities of Kherson and Berdyansk and taken over the towns of Henichesk and an airport near Kherson, the RIA news agency quoted Russia's defence ministry as saying on Sunday.

Russia unleashed a wave of attacks on Ukraine targeting airfields and fuel facilities in what appeared to be the next phase of an invasion that has been slowed by fierce resistance.

The US and EU responded with weapons and ammunition for the outnumbered Ukrainians and powerful sanctions intended to further isolate Moscow.

UN reports at least 240 civilian casualties, 64 deaths in Ukraine

Fuel, cash and medical supplies are running low in parts of Ukraine after Russia's invasion, which could drive up to 5 million people to flee abroad, U.N. aid agencies said on Friday.

At least 100,000 people are uprooted in Ukraine after fleeing their homes since Russia launched its assault on Thursday, while several thousand have already crossed into neighbouring countries including Moldova, Romania and Poland, U.N. refugee agency spokesperson Shabia Mantoo said.

"We are looking at ranges of 1-3 million into Poland for example ... A scenario of 1 to 5 mln including all surrounding countries," Afshan Khan, UNICEF’s regional director for Europe and Central Asia, told a U.N. briefing in Geneva.

UNICEF was focusing on cash assistance to families, she said. The effect of Western sanctions, which have been imposed on Russia, will be analysed in terms of the aid pipeline, she said.

U.N. human rights office spokesperson Ravina Shamdasani said that it had reports of at least 127 civilian casualties in Ukraine - 25 killed and 102 injured - "caused by shelling and airstrikes". This was likely a significant under-estimate, she said.

Jarno Habicht, WHO representative in Ukraine, speaking by video from Kyiv, said that it had no reports from hospitals but was trying to monitor casualties and needs.

The priority is to provide treatment for the wounded as well as mental health and psychological support, he said.

EU foreign affairs ministers are considering cutting Russia's access to the SWIFT system. Exclusion from SWIFT, a very discreet but important cog in the machinery of international finance, is one of the most disruptive sanctions the West has deployed against Russia for its invasion of Ukraine.

The move had been threatened in recent weeks by the United States, the European Union, and other Western allies as a means of escalating the punishment of Russia for its aggression against its ex-Soviet neighbour.

On Saturday, as the Russian military stepped up its assault on Ukrainian cities, Western allies sought to cripple the country's banking sector and currency by cutting selected banks from the international system used to transfer money, severely hamstringing Russia's ability to trade with most of the world.

The measures were backed by the United States, Canada, the European Commission, Britain, France, Germany and Italy. The group of world powers said in a statement it was "resolved to continue imposing costs on Russia that will further isolate Russia from the international financial system and our economies."