Hundreds of thousands of civilians remain trapped and under fire in Ukrainian cities, including besieged Mariupol, following Russia's invasion on February 24.
The first high-level talks between the two sides ended Thursday without any progress in halting a conflict that the UN says has caused 2.5 million people to flee in the worst refugee crisis since World War II.
Russian strikes continued overnight across the country, including on the central city of Dnipro, which local officials said killed one person.
They hit an area near a chemical plant, leaving a shoe factory completely destroyed, and breaking the windows on a nearby kindergarten.
Elsewhere, a care home for disabled people was hit in the village of Oskil, near Kharkiv in eastern Ukraine, in Russian strikes which also destroyed five houses, local officials said.
There were no reports of casualties. At the care home, all 30 staff members and 330 mostly elderly patients -- 10 of whom require wheelchairs -- had been sheltering at the time.
Military targets were also hit early Friday, with four Ukrainian servicemen killed in strikes on the Lutsk military airport in the northwest, local officials said. Moscow said the airfield had been "put out of action".
Meanwhile, the advance of Russian forces continued against the capital Kyiv, which risks being entirely surrounded.
'Nowhere To Run'
The Ukrainian military warned Russia was trying to "block" Kyiv by taking out defences to the west and north of the capital, adding that there was also a risk to Brovary on the east.
Kyiv's mayor Vitali Klitschko said Thursday that half the city's population had fled and the capital "has been transformed into a fortress".
"Every street, every building, every checkpoint has been fortified."
The northwest suburbs, including Irpin and Bucha, have already endured days of heavy bombardment but Russian armoured vehicles are also advancing on the northeastern edge of Kyiv.
Ukrainian soldiers described fierce fighting for control of the main highway leading into the capital, and AFP reporters saw missile strikes in Velyka Dymerka just outside Kyiv's city limits.
"It's frightening, but what can you do?" said Vasyl Popov, a 38-year-old advertising salesman.
"There is nowhere to really run or hide. We live here."
Britain's defence ministry said in an intelligence update that "Russian forces are committing an increased number of their deployed forces to encircle key cities".
"This will reduce the number of forces available to continue their advance and will further slow Russian progress," it said.
The Kremlin said Friday that fighters from Syria and the Middle East would be allowed to fight for Russia in what Moscow calls a "special military operation" in Ukraine.
The Russian army this week admitted conscripts were taking part, after President Vladimir Putin previously said only "professional" soldiers were involved.
Desperation In Mariupol
The southern port city of Mariupol has suffered relentless bombardment, and Ukraine's President Volodymyr Zelensky said attempted aid deliveries had been hit.
He said Moscow had launched a "tank attack" targeting a humanitarian corridor where he had dispatched a convoy to try to get food, water and medicine into the city.
The attack, which Zelensky described in a video statement as "outright terror", came a day after the bombing of a children's hospital there that local officials said killed three people, including a young girl.
Zelensky branded that attack a "war crime", a position backed by top Western officials, while Russia's army claimed the bombing was a "staged provocation" by Ukraine.
In a video, Mariupol mayor Vadym Boichenko said Russian warplanes had targeted residential areas in the city "every 30 minutes" on Thursday, "killing civilians, the elderly, women and children".
The situation in the city has been described as "apocalyptic", with more than 1,200 civilians killed in days of constant attacks, according to the mayor.
The International Committee of the Red Cross said some residents had started fighting for food, and many had run out of drinking water.
Yulia, a 29-year-old teacher who fled Mariupol, said her mother-in-law was still there and told them "the attacks don't stop".
"There are many corpses on the street and nobody buries them," she told AFP.
Some humanitarian corridors out of cities under attack have been held.
Around 100,000 people have been able to leave the northeastern city of Sumy, the eastern city of Izyum, and areas northwest of Kyiv in the last two days, Ukrainian officials said.
Moscow said it would also open daily humanitarian corridors to evacuate civilians to Russian territory, but Kyiv has rejected routes leading to Russia.
'Full-fledged' NATO War
In Turkey, Ukraine's Foreign Minister Dmytro Kuleba said his talks on Thursday with his Russian counterpart Sergei Lavrov ended with "no progress", even on a 24-hour ceasefire.
Lavrov said the two sides would keep talking, but also insisted Russia's invasion was purely defensive.
Asked by a reporter if Moscow was planning to attack other nations, he insisted "we don't plan to attack other countries" and Russia "did not attack Ukraine".
Russia has also ramped up its claims about alleged biological weapons development in Ukraine, which Western officials have said could be an attempt to lay the ground for their possible use by Moscow's forces in the country.
On Friday, the UN Security Council will hold an urgent meeting on the subject at Moscow's request.
A nuclear research facility near Kharkiv was damaged for a second time overnight, local officials said Friday. The UN atomic watchdog previously said the site's inventory of radioactive material is "very low".
Western nations and allies have offered military and humanitarian support, and late Thursday the US congress passed a budget including $14 billion in humanitarian and military aid for Ukraine.
But the US has ruled out enforcing a no-fly zone and rejected a Polish plan to transfer fighter jets to Ukraine via a US airbase for fear of being drawn directly into the conflict.
NATO chief Jens Stoltenberg told AFP Friday the military alliance had "a responsibility to prevent this conflict from escalating beyond Ukraine's borders to becoming a full-fledged war between Russia and NATO".
The European Union meanwhile on Friday proposed to double financing for military aid to Ukraine by an additional 500 million euros ($550 million), which was expected to be backed by EU leaders.