A series of powerful explosions rocked Kyiv early Tuesday even as talks between Ukraine and Russia were set to resume.
At least three large blasts were heard in the centre of the capital early Tuesday, and an AFP journalist saw a column of smoke rising.
The cause was not immediately clear but Ukrainian MP Lesia Vasylenko tweeted a photograph of smoke coming from a damaged block of flats, with firefighters in attendance. Later reports said at least two people were killed.
"Podil district of Kyiv is a place to get coffee and enjoy life. Not anymore. Explosive just hit 30 minutes ago," she said.
Just hours earlier President Volodymyr Zelensky -- wearing his now-signature military-green Tee-shirt -- issued a defiant video address claiming Russia was beginning to realise victory would not come on the battlefield.
"They have already begun to understand that they will not achieve anything by war," Zelensky said, describing the latest round of talks between Ukrainian and Russian negotiators positively.
"Pretty good, as I was told," he said of Monday's first day of discussions. "But let's see. They will continue tomorrow."
The two sides are far apart, with Moscow demanding Ukraine turn away from the West and recognise Moscow-backed breakaway regions.
Ukrainian negotiators say they want "peace, an immediate ceasefire and the withdrawal of Russian troops".
Almost three weeks after vast columns of Russian forces marched across the border, Moscow's forces have bombarded and besieged several Ukrainian towns and cities.
The capital Kyiv is surrounded to the north and east and nearly half its population of three million people have fled.
Only roads to the south remain open, city authorities have set up checkpoints and residents are stockpiling food and medicine.
The United Nations estimates almost 2.8 million people have fled Ukraine and some 636 civilian deaths have been recorded, including dozens of children. The true toll is likely far higher.
- 'Hold back' -
Russia's military progress has been slow and costly, with Moscow apparently underestimating the strength of Ukrainian resistance.
Many military experts believe Russia's military now needs time to regroup and resupply its troops, paving the way for a possible pause or slowdown in fighting.
The head of Russia's national guard Viktor Zolotov has reportedly admitted the operation was "not going as fast as we would like" but said victory would come step-by-step.
Moscow has reportedly turned to Beijing for military and economic help -- prompting what one US official said were several hours of "very candid" talks between high-ranking US and Chinese officials.
Russian President Vladimir Putin has ordered his forces "to hold back on any immediate assault on large cities" according to Kremlin spokesman Dmitry Peskov, who cited "civilian losses" as the reason for stalling an attack.
Russian troops have kept up their siege of southern Mariupol, where officials said nearly 2,200 people have been killed.
In a glimmer of hope for residents of the besieged port city, more than 160 civilian cars were able to leave along a humanitarian evacuation route Monday after several failed attempts.
Meanwhile, Ukraine's allies have piled pressure on Putin's regime with unprecedented economic sanctions, and the Kremlin faces domestic pressure despite widespread censorship of the war.
During Russia's most-watched evening news broadcast on Monday, a dissenting employee entered the studio holding up a poster saying "Stop the war. Don't believe the propaganda."
An opposition protest monitor said the woman, an editor at the tightly-controlled state broadcaster Channel One, was detained following the highly unusual breach of security.
- Shelling in Kyiv -
Across Ukraine, Russia's invasion has continued to take a bloody toll, destroying cities and ensuring that many lives will never be the same again.
"They say that he is too severely burned, that I won't recognise him," sobbed Lidiya Tikhovska, 83, staring at the spot where a paramedic said the remains of her son Vitaliy lay following a missile strike in Kyiv.
"I wish Russia the same grief I feel now," she said, tears rolling down her cheeks as she clung to her grandson's elbow for support.
A correspondent for Fox News -- Britain's Benjamin Hall -- was injured and hospitalized while reporting on the city outskirts, the network said, a day after a US journalist was shot dead in Irpin, a frontline Kyiv suburb.
Meanwhile, Moscow-backed separatists said fragments from a shot-down Ukrainian Tochka-U missile ripped through the centre of the eastern city of Donetsk, killing 23 people.
Moscow called it a "war crime" and rebels published images of bloody corpses strewn in the street.
But Ukraine's army denied firing a missile at the city, with Ukrainian army spokesman Leonid Matyukhin saying in a statement: "It is unmistakably a Russian rocket or another munition."
In neighbouring Lugansk region Ukrainian commander Sergiy Gaiday said the whole Ukrainian-held zone was being bombarded, including "homes, hospitals, schools, water, gas and electricity networks" as well as trains evacuating civilians.
At the other end of the country, in a village outside the western city of Rivne, local authorities said nine people died and another nine were injured when Russian forces hit a television tower.
- 'World War III' -
Ukraine's leader Zelensky on Monday renewed his call for NATO to impose a no-fly zone over his country -- a day after at least 35 people were killed in Russian air strikes near the border with NATO member Poland.
"If you do not close our sky, it is only a matter of time before Russian missiles fall on your territory, on NATO territory, on the homes of NATO citizens," Zelensky warned in a video address.
He is likely to repeat that call Wednesday when he delivers a high-profile virtual address to both chambers of the US Congress.
President Joe Biden and America's NATO allies so far have consistently refused, arguing that any attempt to establish a no-fly zone would place them in direct conflict with nuclear-armed Russia.
Instead, Washington and its EU allies have poured funds and military aid into Ukraine and imposed unprecedented economic sanctions on Russia.
In Biden's words: NATO fighting Russia "is World War III".
United Nations Secretary-General Antonio Guterres sounded the alarm once again on the dangers of a possible showdown between atomic powers -- a prospect "once unthinkable" but "now back within the realm of possibility."
And he warned the war already risked triggering a "meltdown of the global food system" -- with both Ukraine and Russia vital suppliers of wheat to dozens of the world's least developed countries.