Russia has fired two missiles into the Ukrainian capital Kyiv during a visit by United Nations Secretary General Antonio Guterres and one hit the lower floor of a residential building, injuring at least three people, its mayor says.
Reuters could not independently verify the cause of the explosions.
Kyiv has enjoyed relative calm since Russian invasion forces failed to capture it in the face of stiff Ukrainian resistance and withdrew several weeks ago but remains vulnerable to longer-range Russian heavy weaponry.
The blasts shook Kyiv’s central Shevchenko district and the three injured have been hospitalised, Mayor Vitali Klitschko said in a Twitter post.
Defence Minister Oleksii Reznikov and Foreign Minister Dmytro Kuleba both said the blasts were caused by Russian missiles.
Reuters witnesses had earlier reported the sound of two blasts.
The explosions occurred after UN chief Guterres completed talks with Ukrainian President Volodomyr Zelensiky focusing on efforts to allow civilians to leave the Russian-besieged southern port of Mariupol.
Guterres told Portuguese broadcaster RTP when asked about the blasts: “There was an attack on Kyiv…it shocked me, not because I’m here but because Kyiv is a sacred city for Ukrainians and Russians alike.”
Zelenskiy’s chief of staff, Andriy Yermak, said the blasts were “proof that we need a quick victory over Russia… We must act quickly – more weapons, more humanitarian efforts… because every day Ukraine pays a high price for the protection of democracy and freedom”.
Guterres had surveyed the destruction in small towns outside Kyiv on Thursday.
“Wherever there is a war, the highest price is paid by civilians,” Guterres lamented as he visited the bombed-out Kyiv suburb of Irpin.
Responding to repeated Ukrainian pleas for supplies of heavier weaponry and equipment, US President Joe Biden asked Congress on Thursday for $US33 billion ($A46 billion) to support Ukraine, a massive jump in US funding that includes more than $US20 billion for weapons and ammunition and other military aid.
The package, also entailing $US8.5 billion in direct economic assistance and $US3 billion in humanitarian and food security aid, forms part of US efforts to isolate and punish Russia for its February 24 invasion of Ukraine, which has flattened cities and forced more than five million people to flee abroad.
“We need this bill to support Ukraine in its fight for freedom,” Biden said at the White House after signing the request on Thursday.
“The cost of this fight – it’s not cheap – but caving to aggression is going to be more costly.”
The US has said it hopes Ukrainian forces can not only repel Russia’s assault on the east but also weaken its military so that it can no longer menace neighbours.
Russia says that amounts to NATO waging “proxy war” against it and has made a number of threats this week of unspecified retaliation.
Ukraine’s general staff said Russia was stepping up its main military assault in the east, where it now aims to seize all of two provinces partially controlled by separatists.
“The enemy is increasing the pace of the offensive operation. The Russian occupiers are exerting intense fire in almost all directions,” it said.
Russia’s defence ministry said on Thursday the military had fired missiles at six Ukrainian arms and fuel depots and destroyed them, and that 76 Ukrainian military facilities were also hit.
Reuters could not verify the latest battlefield reports.
President Vladimir Putin calls Russian actions a “special military operation” to disarm Ukraine that became necessary as the United States was using the country to threaten Russia and it had to defend Russian-speaking people from persecution.
Ukraine says it is fighting an imperial-style land grab and that Putin’s claims of persecution are nonsense.
Russia has also reported what it says have been a series of Ukrainian strikes on Russian regions which border Ukraine, and has warned that such attacks risk significant escalation.
On Thursday, two big explosions were heard in the Russian city of Belgorod near the border with Ukraine, two witnesses told Reuters.
It was not immediately clear what caused them and whether there were any casualties or damage.
with reporting from AP