The Kremlin said on Tuesday that the war in Ukraine had entered a "different paradigm" due to what it called "inhumane acts of terror" carried out by Kyiv's military against civilians.
Kremlin spokesman Dmitry Peskov made the remarks to reporters when asked about Russia's massive overnight strikes on Ukrainian cities, which killed at least 18 people and wounded 100.
Moscow has said it is stepping up its strikes on military targets in Ukraine in retaliation for what it said was a devastating Ukrainian drone strike on a student dorm in Russian-controlled Luhansk in eastern Ukraine last month, which killed 21 people. Ukraine denies targeting the dorm and said it was targeting a drone command center in the area.
"If the Kyiv regime is consciously committing such inhumane... acts of terror against civilians, against children, then this is an entirely different paradigm," Peskov, the Kremlin spokesman, said.
He said Russia was systematically striking Ukrainian military targets in Kyiv and other cities and that the Ukraine peace process was on hold. Russia remained in touch with the United States, however, he added. Washington has long been trying to broker an agreement between Kyiv and Moscow.
"We remain open to peace negotiations," said Peskov, repeating the Kremlin's stance - which Kyiv says amounts to a demand to capitulate - that the war could end immediately if it agreed to withdraw its forces from four Ukrainian regions Russia claimed as its own in 2022 in what Ukraine said was a bloody land grab.
According to the Ukrainian Air Force, Russia launched 73 missiles and 656 drones over the night in what the Kremlin's defense ministry called a "massive strike" on Ukraine's defense industry facilities using high-precision long-range weapons.
In a statement on Telegram, the Ukrainian Air Force said that 40 missiles and 602 drones had been neutralized.
Ukraine's power infrastructure targeted
Russia has targeted Ukraine's power supply and infrastructure while Ukraine has stepped up attacks this year on Russian oil facilities in a war now more than four years old, sometimes causing casualties, but both deny targeting civilians.
Five people were killed, and 25 were wounded in a Russian missile and drone attack on the southeastern city of Dnipro, regional governor Oleksandr Hanzha said on messaging app Telegram.
All the injured were in hospital in moderate condition, he added, posting pictures of destroyed residential buildings, burnt-out vehicles, and a damaged children's playground.
At least four were killed, and 51 were injured, including children, across the capital of Kyiv, Mayor Vitali Klitschko said.
A suspected missile strike on a 24-story apartment building triggered a collapse, leaving people probably trapped under the rubble, Klitschko said.
A nine-story apartment block was among other buildings set ablaze by suspected missile debris, he added.
"In the Obolon district, cars are burning after being struck by falling missile debris," Klitschko said. "There are also fires at two locations in open areas, including one near a kindergarten."
Thousands of residents flooded into the Kyiv subway system seeking shelter early on Tuesday, witnesses said, some carrying belongings and mattresses, as the sound of defense systems repelling Russian attacks filled the air.
Warnings of a major attack
Air raid warnings sounded over much of the country early on Tuesday after Ukrainian President Volodymyr Zelensky reiterated warnings the previous day of a possible major assault.
"Intelligence warnings regarding Russian strikes remain in effect. A massive strike is possible. They have prepared one," Zelenskiy said in his nightly video address.
"Our defenders are ready 24/7 to the fullest extent possible with the supplies currently available."
Russia warned last week that it intended "systematic strikes" on targets in Kyiv linked to the Ukrainian military as well as decision-making centers, and urged foreigners to leave.
It said the action was in response to a drone strike last month on a dormitory in Ukraine's Russian-held region of Luhansk, which killed 21. Ukraine denied the attack.
In Ukraine's northeastern region of Kharkiv, a child was among 10 injured in drone and missile attacks, Mayor Ihor Terekhov said on Telegram.
Russia's Ilsky oil refinery, in the southern region of Krasnodar, caught fire after a drone attack, local authorities said on Telegram on Tuesday.
Air defense systems were also repelling drone attacks over Sevastopol, a Russian naval fleet base, in Russia-occupied Crimea, authorities there said.
Reuters could not independently verify all the reports.
The Ukraine war has ground on since Russia launched its full-scale invasion in February 2022. Efforts to end it have made little progress, with the administration of US President Donald Trump focused on conflicts in the Middle East.