Updated: 11.50am

Citizens in Kyiv have been urged to prepare Molotov cocktails in an attempt to resist Russian forces approaching the capital amid fears it could fall on the second day of Moscow's offensive.

Vladimir Putin's troops are advancing from the north and northeast, with explosions heard in the capital early Friday that the besieged Ukrainian government described as "horrific rocket strikes".

As Moscow forces arrived in Obolonsky, within the city, the defence ministry urged civilians to resist. 

"We urge citizens to inform us of troop movements, to make Molotov cocktails, and neutralise the enemy," it said.   

The Russian President defied Western warnings on Thursday to unleash a full-scale ground invasion and air assault that quickly claimed dozens of lives and displaced at least 100,000 people.

The United States and its allies responded with a barrage of sanctions, but the Russian forces appeared intent Friday on pressing home their advantage after a string of key strategic victories on day one.

How close is Russia to taking Kyiv?

The soldiers are trying to "bypass" the northern city of Chernigiv -- where they were "rebuffed" -- to attack Kyiv, the Ukrainian army said on Facebook. 

They were also advancing on Kyiv from the eastern city of Konotop, which is under Russian control, Kyiv's army said. 

The Ukrainian army earlier said Russian ground forces had been pushing down the west bank of the Dnieper River from Belarus. 

It said Russian soldiers were "increasingly choosing to target civilian infrastructure and residential buildings", echoing President Volodymyr Zelensky.

An AFP reporter heard explosions and gunfire erupting in the northern part of Kyiv  on Friday, with people running for safety in the city's Obolonsky area. 

The Ukrainian army said Friday it was fighting Russian forces north of the capital in the villages of Dymer -- around 45 kilometres (28 miles) from Kyiv -- and Ivankiv, about 60 kilometres northwest of the city. 

The military claimed to have stopped advancing forces at the Teteriv River outside Kyiv, adding that it had repulsed an attack on the Gostomel airbase. 

137 'heroes' killed

At least 137 "heroes" were killed during the first day of fighting, President Volodymyr Zelensky said on Thursday, as he called up conscripts and reservists nationwide to fight in a general mobilisation.

Zelensky said there was now a "new iron curtain" between Russia and the rest of the world, like in the Cold War, adding in a later speech his nation had been "left alone".

"Who is ready to fight alongside us? I don't see anyone."

And while the United States moved to impose sanctions on Russian elites and banks, it stressed that American forces would not head to eastern Europe to fight in Ukraine.

NATO said it had activated "defence plans" for allied countries.

But NATO chief Jens Stoltenberg said there was no plan to send alliance forces into Ukraine.

'War on Europe'

Among the highest-profile strategic developments on Thursday, Ukraine said Russian forces had seized the Chernobyl nuclear power plant - prompting concern from international nuclear watchdogs.

Zelensky called the attack on Chernobyl "a declaration of war on all of Europe" while 18 people were killed at a military base near the Black Sea port of Odessa in the deadliest single strike reported by Kyiv.

Witnesses also told AFP that Russian paratroopers wrested control of the strategic Gostomel airfield, on the northwestern outskirts of Kyiv.

"The helicopters came in and then the battles started. They were firing machine guns, grenade launchers," resident Sergiy Storozhuk said.

Russian ground forces had initially moved into Ukraine from the north, south and east, forcing many Ukrainians to flee their homes as the sound of bombing reverberated.

Moscow's defence ministry said Thursday its forces had "successfully completed" their objectives for the day, earlier claiming to have destroyed over 70 Ukrainian military targets, including 11 airfields.

Western intelligence confirmed Moscow had established "complete air superiority" over Ukraine.

Ukrainian forces said they had killed "around 50 Russian occupiers" while repulsing an attack on a town on the frontline with Moscow-backed rebels, which could not immediately be confirmed by AFP.

Ukraine also said a military plane with 14 people on board crashed south of Kyiv with officials still determining how many people died, while a transport plane crashed in Russia killing the crew.

Olena Kurilo was among 20 people wounded by flying shards of glass following a blast in the eastern Ukrainian town of Chuguiv.

"Never, under any conditions will I submit to Putin. It is better to die," the 52-year-old teacher said, her face covered in bandages.

In the Ukrainian village of Starognativka near the frontline where separatists have faced off against Kyiv's forces, official Vladimir Vesyelkin said missiles had rained down since Friday morning and power was out.

"They are trying to wipe the village off the face of the earth," he said. 

Sanctions

Weeks of diplomacy failed to deter Putin, who massed over 150,000 troops on Ukraine's borders in what the West said was Europe's biggest military build-up since World War II.

Western allies had initially imposed some sanctions on Russia in an en effort to deter Putin, then followed through on Thursday with vows to try and heavily punish Russia economically.

US President Joe Biden announced export controls against Russia to cut off more than half of the country's high-tech imports, alongside sanctions on Russian elites he called "corrupt billionaires", and banks.

He will meet Friday with fellow Nato leaders in an extraordinary virtual summit to discuss the security situation in and around Ukraine later.

The EU moved to impose "massive" sanctions on Russia's energy and finance sectors, while French President Emmanuel Macron called Putin to "demand immediate halt" to the offensive - but said the door must be kept open for dialogue.

The fighting spooked global financial markets, with stocks plunging and oil prices soaring past $100.

IMF chief Kristalina Georgieva said the unrest carried "significant economic risk" for the world, but Putin insisted he did not seek to undermine the global economic system.

Demonstrations across Europe

In a televised address, the Russian president justified the assault as a defence of the self-proclaimed Donetsk and Lugansk republics in eastern Ukraine.

The Kremlin earlier said the leaders of the two separatist territories had asked Moscow for military help against Kyiv after Putin recognised their independence on Monday.

A conflict between the separatists and government forces has dragged on since 2014, killing more than 14,000 people on both sides.

Russia has also long demanded that Ukraine be forbidden from ever joining NATO and that US troops pull out from Eastern Europe.

In the Baltics, Lithuania declared a national emergency. Latvia, Lithuania and Czech Republic, also stopped issuing visas to Russians.

Demonstrators took to the streets of European capitals to condemn the Kremlin but a small anti-war protest in Moscow was quickly halted by police, with over 1,700 people detained at rallies across Russia.

The first Ukraine refugees have begun to trickle into Hungary, Romania and Poland while the UN said 100,000 had been displaced by the fighting.

"Anyone who can is fleeing," said Krisztian Szavla, one of the first refugees who arrived Thursday in Hungary from Ukraine's western Transcarpathia region.