Air raid sirens are being sounded while explosions were heard before dawn in Kyiv as Ukrainians wake to a new day of Russian attacks.
Ukrainian President Volodymyr Zelenskyy has confirmed pre-dawn missile strikes took place just before 4am (local time) today.
In a video address to the nation, he said Russia had targeted both military and civilian sites.
LIVE UPDATES: Russian forces just kilometres from Kyiv
"Russia will have to talk to us sooner or later about how to end hostilities and stop this invasion," he said.
Meanwhile, the adviser to the Head of the Ministry of Internal Affairs of Ukraine Anton Gerashchenko confirmed the strikes were "cruise or ballistic missiles".
A CNN team on the ground reported hearing two large blasts in central Kyiv and a third loud explosion in the distance.
CNN reporters also said air raid sirens have sounded for several minutes in the nation's capital and Lviv.
9News reporter Carrie Greenbank confirmed she had heard more explosions while live on air.
"We're also hearing the sound of low-flying military jets, we've actually heard of lot of that heading across Kyiv," Greenbank said.
Greenbank also reported Ukrainian forces had claimed to have shot down a Russian aircraft.
She said the forces said the aircraft had been flying over Kyiv and later crashed into a nine-story apartment building.
Greenbank spoke of how she and the team sheltered in a bunker overnight due to the threat of missiles.
"We were sheltering in a bunker as well because at about 1.30am in the morning we got a warning that this central part of Kyiv might face missile strikes," Greenbank said.
Greenbank added she and the team are "on edge".
"We are taking as many precautions as we can in this situation," she said.
"If we have to leave quickly, we will."
Mr Zelenskyy said the government had information that "subversive groups" were encroaching on the city, and US Secretary of State Antony Blinken said Kyiv "could well be under siege" in what US officials believe is a brazen attempt by Russian President Vladimir Putin to dismantle the government and replace it with his own regime.
US Defence Secretary Lloyd Austin told lawmakers on a phone call that Russian mechanised forces that entered from Belarus were about 32 kilometres from Kyiv, according to a person familiar with the call, AP reported.
The Ukrainian military is reporting significant fighting north-west of the nation's capital as Russian forces apparently try to advance on Kyiv from the north.
The military said today a bridge across a river had been destroyed in the area of Ivankiv, about 60 kilometres north-west of Kyiv.
"The hardest day will be today. The enemy's plan is to break through with tank columns from the side of Ivankiv and Chernihiv to Kyiv. Russian tanks burn perfectly when hit by our ATGMs (anti-tank guided missiles)," Mr Gerashchenko said on Telegram.
Ukrainian and US officials said Russian forces were attacking from the east toward Kharkiv, Ukraine's second-largest city; from the southern region of Crimea, which Russia annexed in 2014; and from Belarus to the north.
Ukraine's President slams allies for 'looking on from a distance'
Mr Zelenskyy has made a video address as Ukrainians wake to another day of Russia's invasion.
He has urged resistance to the Russian invasion and criticised Ukraine's allies for the second time in just a few hours.
"This morning, we are defending our country alone," he said in a Facebook video post.
"Just like yesterday, the most powerful country in the world looked on from a distance.
"Russia was hit with sanctions yesterday, but these are not enough to get these foreign troops off our soil.
"Only through solidarity and determination can this be achieved."
Mr Zelenskyy added it was the "second morning of the all-out war".
Full military mobilisation ordered
Mr Zelenskyy has ordered a full military mobilisation to challenge the Russian invasion.
He issued a decree saying the mobilisation would last 90 days.
He ordered the military's General Staff to determine the number of those liable for service and reservists as well as the order of the call-up.
Mr Zelenskyy also said 137 civilians and military personnel have been killed so far in the Russian invasion of his country.
He called them "heroes" in a video address in which he also says hundreds more have been wounded.
Mr Zelenskyy gave his Cabinet the job of allocating funds to pay for the mobilisation.
In a video statement just released, Mr Zelenskyy also said there are enemy sabotage groups in Kyiv, and that he has been identified as Russia's top target.
"According to our information, the enemy marked me as target number one, my family as target number two," Mr Zelenskyy said.
"They want to destroy Ukraine politically by destroying the head of state. We have information that enemy sabotage groups have entered Kyiv."
READ MORE: World expresses outrage, plans stronger Russia sanctions
Males banned from leaving Ukraine
Male Ukrainian citizens aged between 18 and 60 have been prohibited from leaving the country while martial law is in place.
In a statement posted on Facebook, the State Border Guard Service of Ukraine said "departure from Ukraine is restricted" temporarily.
"It is forbidden to travel outside the borders of Ukraine [for] citizens of Ukraine, male gender between 18 to 60 years old," the statement said.
It comes after Russia launched a wide-ranging attack on Ukraine on Thursday (Friday morning AEDT), hitting cities and bases with airstrikes or shelling, as civilians piled into trains and cars to flee.
Speaking live on Ukraine's 1+1 TV channel, Ukraine's Minister of Healthcare Viktor Lyashko said hospitals and medical workers had also come under fire – including in Avdiivka and Vuhledar in Donetsk – with casualties reported among medical workers.
Ukraine's government pleaded for help as it said Russian tanks and troops rolled across the border in a "full-scale war" that could rewrite the geopolitical order.
Mr Putin ignored global condemnation and cascading new sanctions as he unleashed Moscow's most aggressive action since the 1979 Soviet invasion of Afghanistan, and chillingly referred to his country's nuclear arsenal.
He threatened any foreign country trying to interfere with "consequences you have never seen."
'A path of evil': Russia attacks on multiple fronts
Ukrainian officials said their forces were battling Russians on a series of fronts.
"Russia has embarked on a path of evil, but Ukraine is defending itself and won't give up its freedom," Mr Zelenskyy tweeted.
Later, he offered Russia an end to the hostilities.
"It wasn't Ukraine that chose the path of war, but Ukraine is offering to go back to the path of peace," he said.
He said the Russian airborne unit at an airport outside the capital of Kyiv was being destroyed.
The Ukrainian leader said many Russian warplanes and armoured vehicles across the country were destroyed but didn't give numbers.
He also said an unidentified number of Russian troops were taken prisoners.
READ MORE: Russia begins full-scale military invasion of Ukraine
Mr Zelenskyy, who earlier cut diplomatic ties with Moscow and declared martial law, described Russian forces advancing on multiple fronts, including a "difficult situation" developing in Kharkiv, Ukraine's second-largest city, just over 20km away from the eastern border with Russia, and Russian troops slowly advancing from the north on the city of Chernihiv.
He appealed to global leaders, saying that "if you don't help us now, if you fail to offer a powerful assistance to Ukraine, tomorrow the war will knock on your door."
Mr Zelenskyy said Russian forces were trying to seize the Chernobyl nuclear plant, site of the world's worst nuclear disaster, and Ukrainian forces were battling other troops outside Kyiv for control of a strategic airport.
Large explosions were heard in the capital and in other cities yesterday, and people massed in train stations and took to roads, as the government said the former Soviet republic was seeing a long-anticipated invasion from the east, north and south.
US deploys aid to Ukraine
The US Agency for International Development (USAID) has deployed a disaster assistance team to Ukraine in response to Russia's invasion.
The Disaster Assistance Response Team (DART), which contains 17 disaster experts, will be deployed to Ukraine from Poland to lead the US's humanitarian response to the war.
In a statement, USAID said 2.9 million people in Ukraine needed urgent humanitarian assistance before Russia's invasion was launched yesterday, and that 1.5 million had already been displaced due to fighting around separatist regions in the country's east.
Other countries react to the conflict in Ukraine
The chief of the NATO alliance said the "brutal act of war" shattered peace in Europe, joining a chorus of world leaders who decried the attack, which could cause massive casualties, topple Ukraine's democratically elected government and upend the post-Cold War security order.
The conflict was already shaking global financial markets: Stocks plunged and oil prices soared amid concerns that heating bills and food prices would skyrocket.
Condemnation rained down not only from the US and Europe, but from South Korea, Australia and beyond — and many governments readied new sanctions.
READ MORE: Biden condemns 'Russia's unprovoked and unjustified attack' on Ukraine
As the first major world leader to make a big move, UK Prime Minister Boris Johnson announced a freeze on the assets of all large Russian banks and plans to bar Russian companies and the Kremlin from raising money on British markets.
Britain will also ban the export to Russia of a wide range of high-tech products, including semiconductors, and prohibit the nation's flagship airline, Aeroflot, from landing at British airports.
Even friendly leaders like Hungary's Viktor Orban sought to distance themselves from Putin.
While some nervous Europeans speculated about a possible new world war, the US and its NATO partners have so far shown no indication they would join in a war against Russia.
READ MORE: Moment CNN reporter hears loud explosions in Ukraine while live on air
READ MORE: UN chief urges Putin to 'give peace a chance' in Ukraine
They instead mobilised troops and equipment around Ukraine's western flank — as Ukraine pleaded for defence assistance and help protecting its airspace.
In Washington, President Joe Biden convened a meeting of the National Security Council on Ukraine as the US prepares new sanctions.
Biden administration officials have signalled that two of the measures they were considering most strongly include hitting Russia's biggest banks and slapping on new export controls meant to starve Russia's industries and military of US semiconductors and other high-tech components.
