At least 21 civilians, including two children, were killed in a Russian airstrike on a residential street in Ukraine's northeastern city of Sumy late on Monday, the regional prosecutor's office said in a statement on Tuesday.
According to Reuters, the bodies were recovered by emergency services early on Tuesday in searches that are ongoing, it said.
Meanwhile, another Reuters report said, Ukrainians boarded buses to flee the besieged eastern city of Sumy on Tuesday, the first evacuation from a Ukrainian city through a humanitarian corridor agreed with Russia after several failed attempts in recent days.
Sumy governor Dmitro Zhivitskiy said in a video statement that the first buses had already departed Sumy for the city of Poltava, further west. He said priority would be given to the disabled, pregnant women and children in orphanages.
A short video clip released by presidential advisor Kyrolo Tymoshenko showed a red bus with some civilians on board.
"It has been agreed that the first convoy will start at 10 a.m. (0800 GMT) from the city of Sumy. The convoy will be followed by the local population in personal vehicles," Deputy Prime Minister Iryna Vereshchuk said in a televised statement.
Residents were also leaving the town of Irpin, a frontline Kyiv suburb where Reuters journalists had filmed families fleeing for their lives under fierce bombardment on Sunday. Residents ran with their young children in strollers or cradling babies in arms, while others carried pets and plastic bags of belongings.
"The city is almost ruined, and the district where I'm living, it's like there are no houses which were not bombed," said one young mother, holding a baby beneath a blanket, while her daughter stood by her side.
"Yesterday was the hardest bombing, and the lights and sound is so scary, and the whole building is shaking."
Russia's Interfax news agency said Moscow was opening corridors on Tuesday to allow people to leave five Ukrainian cities: Cherhihiv, Kharkiv, Mariupol and the capital Kyiv, as well as Sumy. There was no immediate comment from the Ukrainian side on evacuations from cities apart from Sumy.
Russian and Ukrainian officials had agreed on similar corridors to evacuate residents from the besieged port of Mariupol in the south on Saturday and Sunday, but both those attempts failed, with each side accusing the other of continuing to fire.
Moscow describes its actions in Ukraine as a "special operation" to disarm its neighbour and arrest leaders it calls "neo-Nazis". Ukraine and its Western allies call this a baseless pretext for an invasion to conquer a country of 44 million people.
Russia's invasion, the biggest attack on a European state since World War Two, has sent 1.7 million refugees fleeing to other countries. Western sanctions have cut off Russia from international trade to a degree never before imposed on such a big economy.
