Russia has invited United Nations and Red Cross experts to probe the deaths of dozens of Ukrainian prisoners held by Moscow-backed separatists, while Ukraine's president orders the evacuation of residents in the eastern region of Donetsk.
Ukraine's president Volodymyr Zelensky said hundreds of thousands of people were still exposed to fierce fighting in the Donbas region, which contains Donetsk and Luhansk provinces.
"Many refuse to leave but it still needs to be done," he said in a televised address late on Saturday.
"The more people leave the Donetsk region now, the fewer people the Russian army will have time to kill."
Ukraine and Russia have traded accusations over a missile strike or explosion early on Friday that appeared to have killed dozens of Ukrainian prisoners of war in the front-line town of Olenivka in eastern Donetsk.
Russia invited experts from the UN and Red Cross to probe the deaths "in the interests of conducting an objective investigation", the defence ministry said today.
The ministry had published a list of 50 Ukrainian prisoners of war killed and 73 wounded in what it said was a Ukrainian military strike with a US-made High Mobility Artillery Rocket System (HIMARS).
Ukraine's armed forces denied responsibility, saying Russian artillery had targeted the prison to hide mistreatment there. Foreign Minister Dmytro Kuleba said on Friday that Russia had committed a war crime and called for international condemnation.
Reuters journalists confirmed some of the deaths at the prison, but could not immediately verify the differing versions of events.
The UN had said it was prepared to send experts to investigate if it obtained consent from both parties. The International Committee of the Red Cross said it was seeking access and had offered to help evacuate the wounded.
Ukraine has accused Russia of atrocities against civilians and identified more than 10,000 possible war crimes. Russia denies targeting civilians and war crimes in the invasion it calls a "special operation".
Ukranian counteroffensive
Ukrainian forces attacked the Russian Black Sea Fleet headquarters in the Russian-held Crimean port city of Sevastopol early on Sunday, Sevastopol Governor Mikhail Razvozhayev was quoted by Russian media as saying.
Five members of staff were wounded in the attack when what was presumed to be a drone flew into the courtyard at the headquarters, he said.
Ukrainian authorities said the southern cities of Mykolaiv and Nikopol had been hit by heavy Russian strikes overnight.
Two people were killed and three wounded when 12 missiles hit homes and educational facilities, Mykolaiv Mayor Oleksandr Senkevych told Ukrainian national television, describing the strikes as "probably the most powerful" on the city of the entire war.
Up to 50 Grad rockets hit residential areas in the city of Nikopol on Sunday morning, Dnipropetrovsk Governor Valentyn Reznichenko wrote on Telegram. One person was wounded.
Ukraine's military said on Saturday more than 100 Russian soldiers had been killed and seven tanks destroyed in the south on Friday, including the Kherson region that is the focus of Kyiv's counteroffensive in that part of the country and a key link in Moscow's supply lines.
Rail traffic to Kherson over the Dnipro River had been cut, the military's southern command said, potentially further isolating Russian forces west of the river from supplies in occupied Crimea and the east.
South of the town of Bakhmut, which Russia has cited as a prime target in Donetsk, the Ukrainian military said Russian forces had been "partially successful" in establishing control over the settlement of Semyhirya by storming it from three directions.
Defence and intelligence officials from Britain, which has been one of Ukraine's staunchest allies since Moscow invaded its neighbour on 24 February, portrayed Russian forces as struggling to maintain momentum.
Ukraine has used Western-supplied long-range missile systems to badly damage three bridges across the Dnipro in recent weeks, cutting off Kherson city and - in the assessment of British defence officials - leaving Russia's 49th Army highly vulnerable on the river's west bank.
Reuters could not independently verify the battlefield reports.
Officials from the Russian-appointed administration running the Kherson region earlier this week rejected Western and Ukrainian assessments of the situation.
On Friday the British ministry described the Russian government as "growing desperate", having lost tens of thousands of soldiers in the war. British MI6 foreign intelligence agency chief Richard Moore added on Twitter that Russia was "running out of steam."
Projected harvest halved
Zelensky said today that his country's harvest could be half its usual amount this year due to the Russian invasion.
"Ukrainian harvest this year is under the threat to be twice less," suggesting half as much as usual, he wrote in English on Twitter.
"Our main goal - to prevent global food crisis caused by Russian invasion. Still grains find a way to be delivered alternatively," he added.
Ukraine, a key global supplier of grains, has struggled to get its product to buyers due to a Russian naval blockade of Ukraine's Black Sea ports.
An agreement signed under the stewardship of the UN and Turkey on 22 July provides for safe passage for ships carrying grain out of three southern Ukrainian ports.
Speaking in one of those ports on Friday, Ukraine's infrastructure minister said Ukraine was ready to start shipping grain, and that he was hopeful the first ships would leave by the end of the week.
Putin says Russian navy to get new hypersonic missiles
Russian President Vladimir Putin said on Sunday that the Russian navy would receive hypersonic Zircon cruise missiles within the next few months and that the area of their deployment would depend on Russian interests.
Speaking on Russia's Navy Day in the former imperial capital of St Petersburg, Putin praised Tsar Peter the Great for making Russia a great sea power. Putin did not mention Ukraine directly.
But the Kremlin chief said he had signed a new navy doctrine, the details of which were not published, and touted the Zircon hypersonic cruise missiles as unique in the world.
"The delivery of these (missiles) to the Russian armed forces will start in the coming months," Putin said.
"The Admiral Gorshkov frigate will be the first to go on combat duty with these formidable weapons on board."
"The key thing here is the capability of the Russian navy... It is able to respond with lightning speed to all who decides to infringe on our sovereignty and freedom."
Hypersonic weapons can travel at nine times the speed of sound, and Russia has conducted previous test-launches of the Zircon from warships and submarines over the past year.
- Reuters