US senator Marco Rubio has claimed that “something is off” with Vladimir Putin as invading Russian forces continued to attack Ukraine for the third day.

       “I wish I could share more, but for now I can say it’s pretty obvious to many that something is off with #Putin,” Mr Rubio said on Twitter on Saturday.

       “He [Putin] has always been a killer, but his problem now is different and significant. It would be a mistake to assume this Putin would react the same way he would have 5 years ago,” he said.

       Mr Rubio is a member of the Senate intelligence committee that makes him privy to briefings from American spies.

       Russian forces have launched coordinated missile and artillery attacks on Ukrainian cities, including the capital Kyiv, in Europe’s worst conflict in decades that was launched by Vladimir Putin on Thursday. As the world watched events unfold with shock and horror after Mr Putin’s announcement on Thursday, leaders condemned the invasion and imposed sanctions against Russia.

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       Heavy street fighting against Russian troops is underway in Kyiv as officials urged locals to take immediate shelter. Reuters has reported that Kyiv has been struck by two missiles in the southwest areas of the city centre.

       In another tweet, Mr Rubio said that Russians won’t be happy “when day breaks and they realise that they have been cut off” and surrounded by thousands of upset Ukrainians.

       Earlier on Saturday, he asked the Joe Biden administration to preemptively sanction “anyone who joins a puppet Russian installed government in Ukraine”.

       Those backing Russia’s government should also be handed a visa ban, he said.

       In Kyiv, gunfire erupted near government buildings in the city centre, military officials and witnesses said. A residential tower block more than 20-stories high was hit, and at least five of the apartments were completely destroyed.

       Russia wants to seize control of the Ukrainian capital, according to Ukrainian president Volodymyr Zelensky’s adviser Mykhailo Podolyak. He added that Moscow wanted to destroy the existing leadership.

       Kyiv mayor Vitali Klitschko said dozens were wounded in overnight fighting in the city. At least 35 people, including two children, have been injured in the attacks, the mayor said. It is not immediately clear if the death toll included civilians.

       He added that there was no major Russian military presence in the capital city at present. However, some saboteur groups remained active, Mr Klitschko said.

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       The Russian aggression has been rendered ineffective as it has not made any gains and Ukrainian forces still control the situation in Kyiv, the adviser said.

       Intense fighting is underway in Ukraine’s south in Kherson, just north of Crimea, and in the Black Sea ports of Mykolaiv, Odessa and around Mariupol.