The Russian invasion of Ukraine shifted on the second day to a battle for Kyiv, which shook under a heavy military assault.

The Defence Ministry urged civilians in the capital of three million to make Molotov cocktails to resist the enemy, while the Ukrainian military blew up two bridges to slow the Russian advance.

In Kyiv's northern district of Obolonsky, gunfire and explosions were heard. On social media, videos were posted of Russian armoured vehicles rolling into the city.

Ukraine's President Volodymyr Zelensky said Russian saboteurs had entered Kyiv and that his own life was under threat.

"The enemy marked me as target No. 1 and my family as the target No. 2," he said in a video address.

"They want to destroy Ukraine politically by destroying the head of the state."

He also railed against Europe, saying the sanctions imposed on Russia so far were not enough and urging them to respond faster, while telling Ukrainians not to expect help from abroad.

"We are left to our own devices in defence of our state," he said.

"Who is ready to fight toget-her with us? Honestly, I do not see such."

Attempts by Western countries to send military equipment have been hampered by Russia's control of Ukrainian airspace.

Russian forces also took over the Chernobyl nuclear power station - the site of the world's worst nuclear disaster in 1986 during the Soviet era - which is about 130km north of Kyiv and close to the Belarus border.

Holding Chernobyl would provide Russian troops with a staging point that cannot be shelled.

The invasion was ordered on Thursday by Russian President Vladimir Putin to topple the government and end Ukraine's alignment with the West, which Russia views as a threat to its security.

Chairing a meeting of Russia's security council yesterday, he urged the Ukrainian military to "take power in your own hands" and overthrow the government whose leaders he described as "terrorists" and "a gang of drug addicts and neo-Nazis".

He told Ukraine's army that it would be "easier for us to make a deal with you" than the politicians who had taken "the whole Ukrainian people hostage".

The toll after two days of fighting was unclear, but Mr Zelensky said 137 people had been killed, while other officials put the toll in the hundreds.

The United Nations Security Council was poised to vote early this morning on a draft resolu-tion condemning the invasion and demanding Moscow withdraw its troops.

But its failure to pass was a foregone conclusion, with Russia able to veto it as a permanent member of the council.

In other initiatives under way, the US-led Nato defence alliance held an emergency summit to consider its response to the invasion.

Nato has ruled out deploying combat troops in Ukraine, although it has put its fighter planes and warships on alert.

There were also some uncertain attempts to start talks between Russia and Ukraine.

Support for such talks came from Chinese President Xi Jinping who, in a phone call with Mr Putin, said China is in favour of Russia and Ukraine resolving the issue through negotiation.

A Kremlin spokesman said Mr Putin was willing to take up Mr Zelensky's proposal for talks and Russian officials were prepared to travel to the Belarusian capital Minsk for discussions with Ukrainian representatives.

Ukraine, however, apparently preferred Warsaw, the capital of Poland, as a venue for such talks.

The offer appeared to have been made in response to Mr Zelensky's remarks, in which he urged Russia to come to the negotiating table.

The terms for the talks were unclear, but Russian Foreign Minister Sergei Lavrov said that Moscow was ready for talks if Ukraine's army surrendered.