Russian forces faced stiff resistance from Ukrainians as their invasion of Ukraine continued over the weekend, with Russian forces suffering from logistics problems, according to analysts and the U.S. military.

"They have not achieved what they intended on day four" of the invasion, a senior U.S. defense official told reporters on Sunday, with Ukrainians still in control of all major cities.

However, the situation could quickly change as Russia had only committed about two-thirds of its 150,000 to 190,000 service members who had been stationed around Ukraine as of Sunday, according to the U.S.

Meanwhile, representatives of Ukraine and Russia agreed to talks in Belarus on Monday.

In a speech, Ukrainian President Volodymyr Zelenskyy accused Russia of intentionally targeting civilians and called for an international tribunal to investigate.

"Since the first hours of the invasion, Russian troops have been hitting civilian infrastructure. They consciously chose tactics to destroy people and everything that makes life just normal," Zelenskyy said on Sunday.

Ukraine's interior ministry said at least 352 Ukrainian civilians had been killed, including 14 children, and another 1,684 people have been wounded. Russia has said some of its military members have been killed but has not released numbers, The Associated Press reported.

In New York, the United Nations is set to convene an emergency session of its General Assembly on Monday for only the 11th time in more than 70 years. The emergency session allows all 193 members to debate and vote on a resolution calling for Russia's immediate withdrawal of troops from Ukraine.

And in Russia, President Vladimir Putin ordered what Russia calls its "deterrent forces" on alert, which includes nuclear weapons.

The European Union bans Russian flights and will send weapons

EU Commission President Ursula von der Leyen said on Sunday that Russian-owned, Russian-registered and Russian-controlled aircraft would not be allowed in EU airspace.

"These aircraft will no more be able to land in, take off or overly the territory of the EU," von der Leyen said in a statement.

She also said the EU would "finance the purchase and delivery of weapons and other equipment" to Ukraine, while Germany, Denmark and Sweden over the weekend said they would send weapons and equipment to Ukraine.

The commission also announced new sanctions on President Alexander Lukashenko's regime in Belarus, which is a key ally of Russia.

The U.S. and allies ramp up financial penalties for Russian banks

The U.S., Canada, France, Germany, Italy, the U.K. and the EU Commission also said they would cut certain Russian banks from the SWIFT bank messaging system, which supports millions of secure messages each day to facilitate bank transactions around the world.

"This will ensure that these banks are disconnected from the international financial system and harm their ability to operate globally," the countries said in a statement on Saturday.

The list of banks that will be "de-SWIFTed" has not been finalized.

The countries also say they are working to target Russia's central bank with restrictions to limit Russia's use of $630 billion in foreign currency reserves that it could use to support the ruble.

The U.S. and allies say they've now targeted 10 of Russia's biggest financial institutions.

Protesters across the world stand with Ukraine

From Prague to New York City, Tel Aviv to Tokyo, Buenos Aires to Pretoria, protesters gathered over the weekend to show their support for Ukraine and to condemn Russian President Vladimir Putin.

Some 100,000 people gathered in Berlin on Sunday in front of the city's Brandenburg Gate.

In Russia itself, protesters risked arrest by gathering to voice their opposition to the invasion.

Over 5,900 people in Russia have been detained over four days, according to the human rights monitoring group OVD-Info.

Women and children flee the war

Adult men under 60 have been banned from leaving the country after Zelenskyy declared martial law and instituted a mandatory military conscription.

So at border crossings, long lines of women, children and the elderly are waiting to escape Russia's attacks. At the Medyka border crossing into Poland, a trickle of people came through while tens of thousands were backed up behind them on the Ukrainian side of the border.

As of Sunday, at least 368,000 refugees had crossed into Poland, Hungary, Romania, Moldova and other countries, according to Filippo Grandi, the U.N. high commissioner for refugees.

Humanitarian agencies have warned that millions could leave Ukraine, creating new refugee crisis.

Meanwhile, Ukrainian men who had been living abroad stood in line to return to fight for their country.

Lauren Frayer, Tom Bowman and Becky Sullivan contributed reporting.

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