KYIV (REUTERS) - Russia struck Kyiv with missiles for the first time in more than a month, while President Vladimir Putin warned he would strike new targets in Ukraine if western nations supplied the country with longer-range missiles.

In Sievierodonetsk, the main battlefield in the east where Russia has concentrated its forces recently, Ukraine officials said a counter-attack had retaken half of the city.

Ukrainian President Volodymyr Zelensky said on Sunday (June 5) that he travelled to Lysychansk, south from Sievierodonetsk, and Soledar. The trips were rare outings for him outside the capital since the start of the Russian invasion on Feb 24 and could be the closest to the frontline yet.

"What you all deserve is victory - that is the most important thing. But not at any cost," Mr Zelensky, wearing his trademark khaki T-shirt, told Ukrainian troops in a video released on Sunday night.

Lysychansk and Sievierodonetsk are in the Luhansk region and Soledar is in the Donetsk region. Both regions make up the Donbas, Ukraine's industrial heartland, which Russia claims it is on a mission to "liberate".

In the Kyiv attack, one person was hospitalised though there were no immediate reports of deaths. Dark smoke could be seen from many miles away after Russia's attack on two outlying districts on Sunday.

Ukraine said the strike hit a rail car repair works, while Moscow said it had destroyed tanks sent by Eastern European countries to Ukraine.

Oleksandr Kamyshin, head of the Ukrainian railway, confirmed four missiles had smashed into the Darnytsia rail car repair facility in eastern Kyiv, but said there was no military hardware at the site.

The strike was a sudden reminder of war in Kyiv where normal life has largely returned since Russian forces were driven from its outskirts in March.

The "missile strikes at Kyiv have only one goal - kill as many as possible", Ukrainian presidential adviser Mykhailo Podolyak said on Twitter.

Ukraine said Russia had carried out the Kyiv strike using long-range air-launched missiles fired from heavy bombers as far away as the Caspian Sea.

Ukraine's nuclear power operator said a Russian cruise missile had flown "critically low" over the country's second largest nuclear power plant.

'Cracking them like nuts'

Sunday's attack was the first big strike on Kyiv since late April, when a missile killed a journalist.

Russia has recently focused its destructive might on front lines in the east and south, although occasionally it strikes elsewhere in what it calls a campaign to degrade Ukraine's military infrastructure and block Western arms shipments.

Mr Putin warned the West that Russia would strike new targets if the United States started supplying Ukraine with longer-range missiles, the TASS news agency reported on Sunday.

The United States said last week it would send new, advanced medium-range rocket systems to Ukraine.

In an interview with Russian state television, Mr Putin said the rockets Washington had promised so far were comparable to Soviet-era weapons Ukraine already had.

If Washington were to deliver longer-range rockets, "we will strike at those targets which we have not yet been hitting", he said. He dismissed the impact of Western drones, saying Russia had been "cracking them like nuts".

Britain said it would supply Ukraine with multiple-launch rocket systems that can strike targets up to 80 km (50 miles) away.

Continue to storm Sievierodonetsk

Heavy fighting continues in Sievierodonetsk and Russian forces are pushing towards Sloviansk, Britain’s Ministry of Defence said in a Twitter update.  

However, Governor Gaidai earlier said Ukrainian forces were continuing to push the Russians back from Sievierodonetsk, about 85km (53 miles) east of Sloviansk.  

The claims could not be independently verified. Both sides say they have inflicted huge casualties in Sievierodonetsk.

In Lysychansk, Russian forces fired on a bakery and several administrative and residential buildings, Mr Gaidai said on Monday, adding one civilian had been wounded.

Evacuations resumed from the Ukrainian-held part of Luhansk province on Sunday, and 98 people had escaped, Mr Gaidai said.

A Russian state media journalist on Sunday said Russian Major General Roman Kutuzov had been killed in eastern Ukraine, adding to the string of high-ranking military casualties sustained by Moscow.

The governor of Russia's western Kursk region, Roman Starovoit, said the border village of Tyotkino had come under fire from Ukraine this morning which targeted a bridge and some local businesses. There were no immediate reports of casualties.

Ukraine's military reported that its forces repelled seven attacks in the Donetsk and Luhansk regions on Sunday, destroying four tanks and shooting down a combat helicopter.

Russian forces are "conducting intensive artillery and mortar shelling of our positions" in the Kharkiv region in Donetsk, Ukraine's military general staff said on Monday.

It said Russia was targeting civilian infrastructure in several towns. Moscow denies it targets civilians.

In Donetsk, Russian forces have been advancing in territory north of the Siverskiy Donets river, in advance of what Ukraine anticipates could be a push on the major city of Sloviansk.

In a Sunday address in Rome, Pope Francis called the war "the negation of God's dream".