The drone and missile attack, which targeted Ukraine's energy infrastructure, came as fears are mounting about Moscow's intentions to devastate Ukraine's power generation capacity ahead of the winter.
A Russian strike on a nine-storey building in the city of Sumy in northern Ukraine killed eight people and wounded dozens, an official said on Sunday, as Russia launched a massive drone and missile attack described by officials as the largest in recent months.
Among the eight killed in Sumy, 40 kilometres from the border with Russia, were two children, said Ukraine's Minister of Internal Affairs Ihor Klymenko. More than 400 people were evacuated from the building.
The rescuers were checking every apartment looking for people who might be still in the damaged building.
"Every life destroyed by Russia is a big tragedy," said Klymenko.
The drone and missile attack, which targeted Ukraine's energy infrastructure, came as fears are mounting about Moscow's intentions to devastate Ukraine's power generation capacity ahead of the winter.
Also on Sunday, President Joe Biden authorised for the first time the use of US-supplied long-range missiles by Ukraine to strike inside Russia, after extensive lobbying by Ukrainian officials.
The weapons are likely to be used in response to North Korea's decision to send thousands of troops to support Russia in the Kursk region where Ukraine mounted a military incursion over the summer.
It is the second time the US has permitted the use of Western weapons inside Russian territory within limits after permitting the use of HIMARS systems, a shorter-range weapon, to stem Russia's advance in the Kharkiv region in May.
The first reaction from Ukraine to the long-awaited decision from the US was notably restrained.
"Today, much is being said in the media about us receiving permission for the relevant actions. But strikes are not made with words. Such things are not announced. The missiles will speak for themselves," said Ukraine's President Volodymyr Zelenskyy in his nightly video address.
Earlier, Zelenskyy said Russia had launched a total of 120 missiles and 90 drones in a large-scale attack across Ukraine. Various types of drones were deployed, he said, including Iranian-made Shaheds, as well as cruise, ballistic and aircraft-launched ballistic missiles.
Ukrainian defences shot down 144 out of a total of 210 air targets, Ukraine's air force reported later on Sunday.
"The enemy's target was our energy infrastructure throughout Ukraine. Unfortunately, there is damage to objects from hits and falling debris. In Mykolaiv, as a result of a drone attack, two people were killed and six others were injured, including two children," Zelenskyy said.
Two more people were killed in the Odesa region, where the attack damaged energy infrastructure and disrupted power and water supplies, said local Governor Oleh Kiper. Both victims were employees of Ukraine's state-owned power grid operator, Ukrenergo, the company said hours later.
The combined drone and missile attack was the most powerful in three months, according to the head of Kyiv's City Military Administration, Serhii Popko.
One person was injured after the roof of a five-storey residential building caught fire in Kyiv's historic centre, according to Popko.
A thermal power plant operated by private energy company DTEK was "seriously damaged", the company said.
Russian strikes have hammered Ukraine's power infrastructure since Moscow's all-out invasion of its neighbour in February 2022, prompting repeated emergency power shutdowns and nationwide rolling blackouts. Ukrainian officials have routinely urged Western allies to bolster the country's air defences to counter assaults and allow for repairs.
Explosions were heard across Ukraine on Sunday, including in the capital, Kyiv, the key southern port of Odesa, as well as the country's west and central regions, according to local reports.
The operational command of Poland's armed forces wrote on X that Polish and allied aircraft, including fighter jets, have been mobilised in Polish airspace because of the "massive" Russian attack on neighbouring Ukraine. The steps were aimed to provide safety in Poland's border areas, it said.
Russia's Defence Ministry on Sunday acknowledged carrying out a "mass" missile and drone attack on "critical energy infrastructure" in Ukraine, but claimed all targeted facilities were tied to Kyiv's military industry.
Although Ukraine's nuclear plants were not directly impacted, several electrical substations on which they depend suffered further damage, the UN's nuclear energy watchdog said in a statement on Sunday. According to the International Atomic Energy Agency, only two of Ukraine's nine operational reactors continue to generate power at full capacity.
A local journalist also died on Sunday as Ukrainian drones struck Russia's embattled Kursk region, its Governor Aleksei Smirnov reported.
Moscow's forces have for months strained to dislodge Ukrainian troops from the southern province after a bold incursion in August that constituted the largest attack on Russia since World War II and saw battle-hardened Ukrainian units swiftly take hundreds of square kilometres of territory.
In Russia's Belgorod province, near Ukraine, a man died on the spot after a Ukrainian drone dropped explosives on his car, local Governor Vyacheslav Gladkov reported.
Another Ukrainian drone on Sunday targeted a drone factory in Izhevsk, deep inside Russia, according to anti-Kremlin Russian news channels on the Telegram messaging app.