Russian casualties are likely to be "heavy and greater than anticipated" as Ukrainian Armed Forces put up a staunch resistance, the Ministry of Defence has said.
The bulk of Russian forces involved in the advance on Ukraine's capital Kyiv are now 19 miles from the city centre.
Britain, which earlier disputed reports from Moscow that Russian forces had captured the southeastern city of Melitopol, said the Ukrainian military was continuing to put up staunch resistance across the country.
The night of fighting with heavy shell attacks has taken a great toll on both sides, with estimates suggesting between 1,000 and 3,500 Russian soldiers have been killed.
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"Russia has yet to gain control of the airspace over Ukraine greatly reducing the effectiveness of the Russian Air Force," the defence ministry said in an intelligence update posted on Twitter.
The updated stated: "Russian casualties are likely to be heavy and greater than anticipated or acknowledged by the Kremlin."
During a press briefing this morning, passionate Ukrainian President Volodymyr Zelenskiy said the country's troops were holding Russian forces back.
He said: “Please stop those who are lying, or trying to lie to you, or lying to us. We need to stop this war. We can live in peace together, globally as humans.
“Our military, our national guard, our national police, our territory defence, special service, nationals of Ukraine, please carry on. We will win. Glory to Ukraine.”
It comes as Western officials have expressed fears that Russia could unleash a terrifying new weapon which would decimate Ukraine as the conflict deepens.
They fear Vladimir Putin could use devastating thermobaric rockets on the people of Kyiv, after they have shown fierce resistance to the Russian invasion.
Zelenskiy added: “We are successfully holding back the enemies attacks. We know we are defending our land and the future of our children. Kyiv and the key areas are controlled by our army.
“The occupiers wanted to set up their puppet in our capital. They didn’t succeed. On our streets, there was a proper fight going on.
"The enemy was using all its weapons, artillery, paratroops, all its weapons. They are hitting residential areas, they are trying to destroy energy infrastructure, and everyone should help us to stop this occupation."
While Russian troops attempt to take the city of Melitopol in the southeastern Zaporizhzhya region, a combination of trained troops and civilians baring arms have managed to stave off attacks in most other areas with the bulk of Putin's forces around 20 miles from the centre of Kyiv.
Putin has meanwhile threatened Sweden and Finland with 'military and political consequences' if they join NATO.
Maria Zakharova, Russia's foreign ministry spokeswoman, says there will be serious repercussions for their close Arctic neighbours.
Both Scandinavian nations share a border with Russia.
Zakharova said during a news briefing: "Finland and Sweden should not base their security on damaging the security of other countries and their accession to NATO can have detrimental consequences and face some military and political consequences."
