By Natalia Zinets

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 U.N. chief Guterres completed talks with Ukrainian President Volodomyr Zelensiky focusing on efforts to evacuate civilians from 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.”

Responding to repeated Ukrainian pleas to Western leaders for supplies of heavier weaponry and equipment, U.S. President Joe Biden asked Congress on Thursday for $33 billion to support Kyiv, a massive jump in U.S. funding that includes over $20 billion for weapons and ammunition and other military aid.

The package, also entailing $8.5 billion in direct economic assistance and $3 billion in humanitarian and food security aid, forms part of U.S. efforts to isolate and punish Russia for its Feb. 24 invasion of Ukraine, which has flattened cities and forced more than 5 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.” Read full story

Washington 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.

After being beaten back in efforts to capture Kyiv in the north, Russia has shifted forces hundreds of miles eastward to capture two provinces in a battle the West believe may prove a decisive turning point in the war.

Russian forces are now entrenched in the east, where Moscow-backed separatists have held some territory since 2014, and also hold a swathe of the south they seized in March.

‘SHAM REFERENDA’

The U.S. mission to the OSCE security body said the Kremlin might attempt “sham referenda” in southern and eastern areas it had captured since the Feb. 24 invasion, using “a well-worn playbook that steals from history’s darkest chapters”.

“These falsified, illegitimate referenda will undoubtedly be accompanied by a wave of abuses against those who seek to oppose or undermine Moscow’s plans,” the U.S. mission said.

Ukraine reported blasts overnight in the southern city of Kherson, the only regional capital Russia has captured so far since the invasion. Russian troops there had used tear gas and stun grenades on Wednesday to quell pro-Ukrainian crowds, and were now shelling the entire surrounding region and attacking towards Mykolaiv and Kryvyi Rih, Ukrainian officials said.

Russian state media quoted an official from a self-styled pro-Russian “military-civilian commission” in Kherson on Thursday as saying the area would start using Russia’s rouble currency from May 1.

Ukraine accused Russia on Thursday of stealing grain in the Kherson region, an act which it said raised the threat to global food security posed by disruptions to spring sowing and the blocking of Ukrainian ports during the war. Read full story

EMBATTLED EAST

Ukraine’s general staff said Russia was also stepping up its main military assault in the east, where Moscow 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 Moscow 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.

WEST STEPPING UP MILITARY AID

Western countries have ramped up weapons supplies to Ukraine in recent days as the fighting in the east has escalated.

More than 40 countries met this week at a U.S. air base in Germany and pledged to send heavy arms such as artillery for what is expected to be a vast battle of opposing armies along a heavily fortified front line on open, flat terrain.

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.

Ukraine has not directly accepted responsibility for strikes inside Russia but says the incidents are payback, while Russia has taken umbrage at statements from NATO member Britain that it is legitimate for Ukraine to target Russian logistics.

“In the West, they are openly calling on Kyiv to attack Russia including with the use of weapons received from NATO countries,” Russian Foreign Ministry spokeswoman Maria Zakharova told reporters in Moscow.

“I don’t advise you to test our patience further.”

(Additional reporting by Reuters journalists; Writing by Peter Graff and Mark Heinrich; Editing by Angus MacSwan and Toby Chopra)