Ukrainian forces continued to resist Russia's advance into Kyiv overnight, though explosions rang out continually and gunfire could be heard from the city center.

President Volodymyr Zelensky remained resolute — and physically present in his nation's capital — telling Ukrainians to "stand our ground" as "the fate of Ukraine is being decided now."

The latest: "The enemy will use all of their power on all fronts to break our defense," Zelensky said in his address, adding that "many cities are under threat: Chernihiv, Sumy, Kharkiv, Donbass, southern Ukraine and special attention to Kyiv.”

Fears that the fall of Kyiv could be imminent increased after Russian troops entered the city's northern outskirts on Friday and Zelensky warned that Russia intended to storm the city overnight.

Zelensky posted a video of himself and his aides in Kyiv's government district earlier on Friday to tamp down rumors that he had fled. "We are here. We are in Kyiv. We are defending Ukraine," Zelensky said.

President Biden, who will meet with his national security team on Saturday morning, said Friday afternoon that he spoke with Zelensky and "commended the brave actions of the Ukrainian people who were fighting to defend their country."

The Biden administration also asked Congress to provide $6.4 billion in funding to assist Ukraine and the request is likely to receive bipartisan support. "We’re looking at including a Ukraine assistance package and COVID relief in the omnibus," a congressional leadership aide told Axios on Friday.

State of play: The U.S. joined the European Union and United Kingdom in imposing sanctions Friday on Russian President Vladimir Putin.

"It is exceedingly rare for Treasury to designate a head of state; President Putin joins a very small group that includes despots such as Kim Jong Un, Alyaksandr Lukashenka, and Bashar al-Assad," the U.S. Treasury Department said in announcing the sanctions.

The Kremlin had previously said it would consider sanctions on Putin himself to be a de facto severing of relations between the U.S. and Russia.

At the United Nations, 87 countries either voted for or co-sponsored a draft UN Security Council resolution deploring Russia's invasion of Ukraine on Friday, though Russia used its veto to block it.

Thousands of people around the world are coming out to show their support for Ukraine with rallies documented in countries ranging from Thailand and Greece to the former Soviet republic of Georgia and Russia itself.

Thousands of Georgians — who themselves came under attack from Russia in 2008 — poured into the streets Thursday and Friday to protest their government's inaction following Russia's invasion of Ukraine.

What's happening: Russian President Vladimir Putin called on the Ukrainian military to overthrow the government and "take power into your own hands" — explicitly demanding regime change as a precondition for peace talks.

A Pentagon official told reporters Friday: "The Russians have lost a little bit of their momentum. No population centers have been taken. Russia has yet to achieve air superiority." The official cautioned that Russia has only deployed one-third of its forces massed on the border and could still overwhelm Ukraine.

NATO has activated elements of its 40,000-troops NATO Response Force for the first time in history, deploying them to eastern flank countries, with Secretary-General Jens Stoltenberg warning that "the Kremlin's objectives are not limited to Ukraine."

Still, defense analysts note that the Russian military exceeds the capabilities of Ukraine's on all fronts, and that thus far only about one-third of the Russian troops massed for the operation have entered the fray.

What to watch: Russia has also not unleashed the full force of its cyber capabilities, which could shut down key Ukrainian infrastructure.