Russian airstrikes hit a blood transfusion center in the town of Kupiansk in eastern Kharkiv region late Saturday.
"There are dead and wounded," Ukrainian President Volodymyr Zelenskyy said on his Telegram channel. Kupiansk is a railway hub within 10 miles of the front.
Zelenskyy said rescue workers were extinguishing a fire at the scene and described the strike as a "war crime." He did not say how many people were killed or wounded.
Russia denies deliberately targeting civilians in a full-scale invasion that has killed thousands of people, uprooted millions and destroyed cities.
Reuters could not immediately verify the report.
Earlier, Russia vowed retaliatory strikes for Ukraine drone attacks against two Russia ships within 24 hours.
Senior officials from 42 countries concluded the first day of the two-day Jeddah peace summit on Ukraine.
According to officials, no final declarations will be released. Instead, Saudi Arabia, hosting the summit at its port of Jeddah, would present a plan for further talks, with working groups to discuss issues such as global food security, nuclear safety and prisoner releases.
A European official described the talks as positive and said there was "agreement that respect of territorial integrity and (the) sovereignty of Ukraine needs to be at the heart of any peace settlement."
The high-level talks included delegates from the world economies of the BRICS group, Brazil, India, China and South Africa, but not Russia. It said it will not be involved in these talks or the summit planned for the fall.
The head of Brazil's delegation, foreign policy adviser Celso Amorim, stressed however, that "any real negotiation must include all parties," including Russia, according to a copy of his statement shared with AFP.
"Although Ukraine is the biggest victim, if we really want peace, we have to involve Moscow in this process in some form," he said.
China, a neutral party in the conflict, announced Friday that its special representative for Eurasian affairs, Li Hui, would attend.
U.S. national security adviser Jake Sullivan led Washington's delegation, a senior White House official said.
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Ukraine and Western diplomats expressed hope that the meeting would be an opportunity for officials to agree on key principles to inform any peace agreement that would end Russia’s ongoing war in Ukraine.
Ukraine anticipated disagreements during the two-day summit, but the head of Ukraine’s presidential office, Andriy Yermak, said Friday that it is important “to share our principles.”
Western officials and analysts said Saudi diplomacy had been important in securing China's presence at the talks.
Under the leadership of Crown Prince Mohammed bin Salman, the kingdom has kept ties with both sides presenting itself as a mediator and seeking a bigger role on the world stage.
In his nightly video address, Zelenskyy commented “the greater the consolidation of the world for the sake of restoring a just peace is, the sooner an end will be put to the bombs and missiles with which Moscow wants to replace the norms of international law.”
Beyond its Western backers, Ukraine hopes to garner diplomatic support from more Global South countries, including Brazil, India, South Africa and Turkey.
Part of Ukraine’s strategy to gain support from such countries reportedly will be to emphasize how food prices have risen after Russia quit the U.N.-brokered Black Sea grain deal last month and began attacking Ukrainian port facilities.
Russia condemned a Ukrainian strike on one of its civilian vessels in the Kerch Strait near the strategic bridge that links Crimea with Russia’s mainland.
Calling it a “terrorist attack,” Russian Foreign Ministry spokesperson Maria Zakharova said Saturday that Russia will respond and punish those responsible.
Former Russian President Dmitry Medvedev suggested Saturday that Moscow would launch retaliatory strikes against Ukrainian ports in response to Kyiv's attacks on Russian ships in the Black Sea.
Ukraine has unofficially claimed responsibility for the attack, the second in 24 hours. An anonymous security service source told Agence France-Presse that the SIG tanker is “one of the most powerful oil tankers of the Russian Federation,” adding that “it was well-loaded with fuel, so ‘fireworks’ could be seen from afar.”
Russian maritime officials confirmed Saturday the Ukrainian sea drone attack has damaged the Russian tanker, suspending traffic and ferry transport services in the area.
According to Russian media reports, the tanker was hit by Ukrainian drones as it was approaching the Kerch Strait that links the Black Sea and the Sea of Azov.