• Moscow has recently increased strikes on Ukraine's energy infrastructure, leaving half of the country's power grid in need of repair.
• Across the border, Moldova also reported "massive" blackouts, although it has not been directly hit.
Ukraine's western city of Lviv is without power after a wave of Russian missiles pounded the country.
Critical infrastructure in Kyiv was also targeted, and the city's officials said three people died in the attack.
Across the border, Moldova also reported "massive" blackouts, although it has not been directly hit.
Moscow has recently increased strikes on Ukraine's energy infrastructure, leaving half of the country's power grid in need of repair.
Ukraine's national power grid operator has said the damage sustained by power generating facilities in recent weeks has been "colossal" and warned that Ukrainians could face long power outages over the winter months.
Early on Wednesday, an air-raid alert was issued across Ukraine, followed by reports of explosions in a number of locations.
Ukraine's air force said over 70 cruise missiles were launched by Moscow, with air defences intercepting 51 projectiles. Officials said five drones were also launched.
But the attack has caused significant damage to infrastructure across the country.
Ukraine's state energy company, Energoatom, said three nuclear reactors were taken offline due to the blackout.
And in the capital Kyiv, parts of the city have been let without water and completely without power, Mayor Vitali Klitschko said.
Lviv mayor, Andriy Sadovy, said children had been taken to shelters with their teachers - and urged parents not to pick them up until the alarm was over.
Shortly before the fresh reports from Kyiv and Lviv, officials said southern Ukraine had come under renewed assault.
The governor of the Mykolaiv region warned of "many rockets" arriving from the south and east.
In the nearby Zaporizhzhia region, a newborn baby was killed when a missile hit a maternity unit, emergency services said.
Russia was blamed for that attack, but is yet to comment on any of Wednesday's alleged strikes.
Blackouts in Moldova
More than half of Moldova was also left without electricity, deputy prime minister Andrei Spinu wrote on Twitter. He said the attack on Ukraine's energy infrastructure has caused a "massive blackout" across Moldova.
Within a few hours power was starting to be restored in the Moldovan capital Chisinau, a Reuters journalist reported.
Moldova also experienced widespread power cuts as a result of strikes on Ukraine on 15 November, Mr Spinu said. Mobile networks were also badly affected.
Sergiu Tofilat, a local energy policy analyst, told Moldova's TV8 channel that the country's energy supplies relied on a power line that passed through Transnistria, a breakaway Russian-controlled territory in Moldova bordering Ukraine, before reaching the capital Chisinau.
"When there are bombings in Ukraine, this line is automatically disconnected and we are left without electricity," he was quoted as saying.
In response to the outages, Moldovan President Maia Sandu said Russia had "left Moldova in the dark".
"Russia's war in Ukraine kills people, destroys residential blocks and energy infrastructure with missiles..." she wrote on Facebook. "But the electricity supply can be restored. We will solve the technical problems and we will have light again. All state institutions are working in this direction."