Ukrainian President Volodymyr Zelensky has warned Russian forces they face a fight to the death if they try to occupy the capital Kyiv, as air raid sirens again woke residents on Sunday morning.
"If they decide to carpet bomb and simply erase the history of this region ... and destroy all of us, then they will enter Kyiv. If that's their goal, let them come in, but they will have to live on this land by themselves," Zelensky said on Saturday.
The president, who has repeatedly appeared on social media from the capital, said some small towns no longer existed in the third week of Russian attacks, the biggest assault on a European country since World War Two.
Russian shelling has trapped thousands of people in besieged cities and sent 2.5 million Ukrainians fleeing to neighboring countries.
Seven civilians dead after Russia attacks convoy
The seven women and children who Ukraine says died when Russian forces attacked a convoy escaping a village in the Kyiv region were not as previously stated in an agreed evacuation corridor, the defense ministry said on Saturday.
Ukraine's intelligence service initially said those who died outside Peremoha on Friday had been in a "green corridor" agreed with Russia. A defense ministry statement later said people had in fact tried to escape by themselves, "so they began evacuating without the 'green corridor' agreed by the parties."
The eastern Ukrainian town of Volnovakha has been completely destroyed following the Russian invasion but fighting continues for territory there to prevent a Russian encirclement, Donetsk governor Pavlo Kyrylenko said on Saturday.
Around 1,300 Ukrainian troops have been killed since the start of the Russian invasion, President Volodymyr Zelensky said on Saturday.
Speaking at a news briefing, Zelensky said Ukrainian and Russian negotiating teams had started discussing concrete topics rather than exchanging ultimatums.
Air raid sirens blared across most Ukrainian cities on Saturday morning urging people to seek shelters, local media reported.
The exhausted-looking governor of Chernihiv, around 150 km (100 miles) northeast of Kyiv, gave a video update in front of the ruins of its Ukraine Hotel, which he said had been hit on Saturday.
"There is no such hotel anymore," Viacheslav Chaus said, wiping tears from his eyes. "But Ukraine itself still exists, and it will prevail."
Russian rocket attacks destroyed a Ukrainian airbase and hit an ammunition depot near the town of Vasylkiv in the Kyiv region on Saturday morning, Interfax Ukraine quoted Vasylkiv Mayor Natalia Balasynovych as saying.
Moscow has denied targeting civilians what it calls a special operation to demilitarize Ukraine and unseat leaders it refers to as neo-Nazis. It has not responded to Ukrainian challenges to provide evidence.
Ukraine said it expected a new wave of attacks on the regions around the capital Kyiv, the country's second city Kharkiv and Donbass in the east, where Russian-backed separatists have expanded their control.
Britain's defense ministry said on Friday that Russian forces could launch an offensive on Kyiv in a few days. In an update on Saturday, it said fighting northwest of the capital continued, with the bulk of Russian ground forces 25 km (16 miles) from the center.
The cities of Kharkiv, Chernihiv, Sumy and Mariupol remained encircled under heavy Russian shelling, it said.
Close Russian ally Belarus said it was sending five battalion tactical groups to its border with Ukraine but had no plans to send troops into Russian forces fighting there.
A top Ukrainian security official on Friday warned Belarus not to send troops to Ukraine, saying Ukraine was showing restraint towards Belarus despite the country being used as a launchpad for Russian planes.
Belarus Chief of General Staff Viktor Gulevich said the battalion tactical groups would replace forces already stationed near the border.
“I want to underline that the transfer of troops is in no way connected with (any) preparation, and especially not with the participation of Belarusian soldiers in the special military operation on the territory of Ukraine,” Gulevich said.
Russia repeatedly denied any plan to invade Ukraine before it invaded by land, air and sea.
Russian forces have shelled a mosque in the southern Ukrainian port city of Mariupol, where more than 80 adults and children, including Turkish citizens, have taken refuge, Ukraine's foreign ministry said on Saturday.
Ukraine has accused Russia of refusing to allow people out of Mariupol, where a blockade has left hundreds of thousands trapped. Moscow blames Kyiv for its failure to evacuate people.
"The mosque of Sultan Suleiman the Magnificent and his wife Roxolana (Hurrem Sultan) in Mariupol was shelled by Russian invaders," the foreign ministry said in a tweet. "More than 80 adults and children are hiding there from the shelling, including citizens of Turkey."
It did not say if there were any people killed or wounded.
Moscow has denied targeting civilian areas in what it calls a "special military operation" in Ukraine.
Russia is prepared to resume arms control talks with the United States if America is, Russian Deputy Foreign Minister Sergei Ryabkov said, according to RIA news agency.
Moscow and Washington remain in constant contact, he said, but that the Kremlin sees no signs that the US is ready to continue a dialogue on Ukraine.
Ryabkov said proposals on security guarantees that Russia had sent to the United States and NATO before its forces entered Ukraine last month were no longer valid, since the situation had now changed completely.
Russian attacks continue during latest evacuation attempts
The governors of two Ukrainian regions, Kyiv and Donetsk, said in separate statements on Saturday that Russian attacks were continuing in areas where Ukraine was trying to evacuate people and bring aid through "humanitarian corridors."
"Humanitarian cargo is moving towards Mariupol, we will inform you how it develops ... The situation is complicated, there is constant shelling," Donetsk Governor Pavlo Kyrylenko told local media. "The situation is extremely difficult."
Ukrainian refugees
Germany will take in 2,500 refugees who have fled to Moldova from Ukraine, Foreign Minister Annalena Baerbock said on Saturday, as eastern Europe's efforts to aid refugees come under strain.
The number of refugees who have fled Ukraine since Russia launched its invasion on February 24 now totals more than 2.5 million and some cities in eastern Europe are running out of accommodation.
After meeting her Moldovan counterpart in Chisinau, Baerbock said Germany was committed to helping Ukraine's neighbors look after refugees and that a corridor would be set up via Romania to bring people to Germany, mainly by bus.
"Europe and our country stand in solidarity with you; we will take refugees from you," she said.
More than 270,300 people have crossed into Moldova from Ukraine and around 105,000 of them have stayed.
In Germany, some 109,183 refugees have so far been registered, the interior ministry said on Friday, and Germans have offered up to 300,000 private homes to house them.