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The Russian President said Moscow would strike new targets if the United States started supplying Ukraine with longer-range missiles, the Russian TASS news agency reported.

At least one person was taken to hospital following the explosions but no deaths had been reported as of early Sunday, Vitali Klitschko said.

Ukrainian officials said Russia was targeting Kyiv's railway infrastructure, but Moscow has claimed it destroyed T-72 tanks supplied to Ukraine from eastern Europe.

In eastern Ukraine where the bulk of the fighting has been focused in recent weeks, Luhansk Governor Serhiy Haidai said Russian forces have been pushed back in Severodonetsk.

Control of the contested factory city was now "more or less, divided in half", he said.

Meanwhile, Spain is preparing to send heavy weapons to Ukraine, including anti-aircraft missiles and Leopard battle tanks, El Pais reports.

Key developments:

• Ukrainian forces counterattack in Severodonetsk
• Macron causes controversy with call not to "humiliate" Moscow
• Russian shelling killed at least three civilians in the Black Sea port city of Mykolaiv, mayor says

Explosions heard in Kyiv

Dark smoke rose into the sky as the sun dawned on Kyiv on Sunday morning after the Darnytskyi and
Dniprovskyi districts were hit by explosions, the city's mayor Vitaly Klitschko said.

"According to preliminary data, the (Russians) launched missiles from Tu-95 aircraft from the Caspian Sea", the Ukrainian air forces said in a statement.

The missiles were the first to hit the capital since late April when a Radio Liberty producer was killed when a Russian missile hit the building she lived in.

Posting on Telegram, Mr Klitschko said the blasts were heard in the districts of Darnytsky and Dniprovsky.

"There are currently no casualties from missile strikes on infrastructure," he wrote.

"One injured person was hospitalised. The services are still working in the affected areas."

Ukrainian presidential advisor Mykhailo Podolyak said the bombardment was Russia resorting to "new insidious attacks" and hit out at French President Emmanuel Macron's statement that Moscow should not be humiliated.

Moscow claims strike destroyed tanks provided by Ukraine's allies

The Russian Defense Ministry said high-precision, long-range air-launched missiles were used and the strikes destroyed T-72 tanks supplied by Eastern European countries located in buildings of a train car repair business.

The head of Ukraine's railway system rejected the claim that tanks were inside.

President Putin, in excerpts of an upcoming interview quoted by Russian news agencies, said that if the West supplies
longer-range missiles to Ukraine "we will strike at those targets which we have not yet been hitting".

His threat of a military escalation did not specify what the new targets might be, but it comes days after the United States announced plans to deliver $700 million of security assistance for Ukraine.

Those weapons include four precision-guided, medium-range rocket systems, helicopters, Javelin anti-tank weapon systems, radars, tactical vehicles and more.

Fierce fighting continues in Donbas region

Meanwhile, fighting continues in the southeastern areas of Donetsk and Luhansk, the focus of the Russian army since it withdrew from Ukraine's capital Kyiv.

Ukrainian forces have counterattacked in the factory city of Severodonetsk and claim to have retaken territory from Russian troops.

Serhiy Haidai, Governor of Luhansk province, said on Sunday Ukrainian forces controlled about half the city after recapturing a large portion from Russian troops.

"It had been a difficult situation, the Russians controlled 70% of the city, but over the past two days they have been
pushed back," he said on Ukrainian television.

UK MoD: Russia using proxy troops in Severodonetsk to limit military losses

Britain's Ministry of Defence (MoD) said Ukraine's counterattack was "likely blunting the operational momentum Russian forces previously gained through concentrating combat units and firepower".

They added that Kremlin forces in the area include "poorly equipped and trained" separatist troops lacking in heavy equipment, likely part of a desire to limit casualties suffered by the regular Russian military.

If Russia was to take Severodonetsk and Lysychansk, the province of Luhansk would be under Moscow's control, and the entire Donbas region - which includes Luhansk and Donetsk - would be within its grasp.

Ukraine's president Volodymyr Zelenskyy said on Saturday night: "The situation remains very difficult in Severodonetsk, where street fighting is ongoing."

'We must stop Russia'

Speaking at an international security forum last week, defence minister Oleksiy Reznikov said: "Russia continues to make efforts to occupy our entire state.

"It is currently impossible to predict when the war will end, but my optimistic predictions are that it will be possible to do it this year."

Mr Reznikov warned that, until the Russians are forced out of Ukraine, other countries are also at risk, saying: "Next will be Poland, the Baltic countries, Slovakia, and others.

"That is why we must stop Russia and restrain (them) in the future."

His warning over Russia's ambitions came after President Macron was criticised for saying that Moscow must not be "humiliated" over the invasion of its neighbour.

In an interview with a regional newspaper, Mr Macron said: "We must not humiliate Russia so that the day when the fighting stops we can build an exit ramp through diplomatic means."

In response, Ukraine's foreign minister Dmytro Kuleba tweeted: "Calls to avoid humiliation of Russia can only humiliate France and every other country that would call for it."

He added: "We all better focus on how to put Russia in its place."

Read more:
Children with toy guns manning checkpoints, while body hunters search for dead Russian soldiers

Elsewhere this weekend, Russian shelling killed at least three civilians in the Black Sea port city of Mykolaiv, mayor Oleksandr Senkevich said.

Russian shelling and a fire contributed to the destruction of a 16th century timber Orthodox Christian monastery in eastern Ukraine, killing two monks and a nun.

And the number of bodies of civilians that have been exhumed in the Kyiv region since Russia's military retreat now stands at more than 1,300, according to Ukraine's interior ministry.