Ukraine also insisted Saturday that the fighting in Soledar was continuing, a day after Russia's claim that it had captured the ravaged eastern town following a long battle.
Victory there would be a rare achievement for Moscow after a series of military setbacks.
Ukrainian officials denounced the latest wave of deadly Russian missiles strikes across the country, as the country celebrated the Old New Year, a popular holiday in Ukraine.
At least 14 people, including a 15-year-old girl, were killed and 64 wounded when an apartment building was hit in the eastern city of Dnipro, Dnipropetrovsk governor Valentyn Reznichenko said on messaging app Telegram.
Seven children were among the wounded, the youngest three years old, he added.
So far 38 people had been pulled from the rubble and the search operation was continuing, he said.
Rescuers were also working through the night to free a woman trapped under the rubble of a destroyed house in Dnipro after hearing her voice, the state emergency service said.
The strike on the Dnipro apartment block destroyed dozens of flats, leaving between 100 and 200 people homeless while around 1,700 were without electricity and heating, the deputy head of presidency Kyrylo Tymoshenko said.
UK sending first heavy tanks
Earlier Saturday, British Prime Minister Rishi Sunak pledged to provide Challenger 2 tanks to Ukraine, the first Western country to supply the heavy tanks Kyiv has been crying out for.
The tanks would arrive in Ukraine in the coming weeks, Sunak's Downing Street office said in a later statement, adding that Britain would also begin training the Ukrainian Armed Forces to use the tanks and guns.
Russia's embassy in the UK swiftly issued a warning that “bringing tanks to the conflict zone, far from drawing the hostilities to a close, will only serve to intensify combat operations, generating more casualties, including among the civilian population”.
But in his evening address on Saturday, Zelensky argued that Russian “terror” could only be stopped on the battlefield.
“This can and must be done on our land, in our sky, in our sea,” he said.
Moldova, Ukraine's southwestern neighbour, said Saturday it had found missile debris on its territory after the latest Russian strikes.
“Russia's brutal war against Ukraine directly impacts Moldova again,” President Maia Sandu tweeted, posting photos of the wreckage.
“We strongly condemn today's intensified attacks.”
Energy infrastructure hit
Ukraine's energy facilities operator Ukrenergo said it was working on “eliminating the consequences” of the latest Russian strikes. In Kyiv, AFP journalists heard several explosions, while Ukrainian officials reported strikes on a power facility.
“There is a hit to an infrastructure facility, without critical destruction or fire,” the Kyiv city administration said.
In the northeastern Kharkiv region, “the enemy launched another missile attack on critical infrastructure and industrial facilities,” governor Oleg Synegubov said.
Emergency blackouts were applied in “most regions” of Ukraine due to the fresh barrage of attacks, energy minister German Galushchenko said Saturday.
Attacks were also reported in the southern Zaporizhzhia region.
Zelensky said Ukraine had managed to shoot down 20 of the more than 30 Russian missiles fired.
“Unfortunately, energy infrastructure facilities have been also hit,” he added, with the Kharkiv and Kyiv regions suffering the most.
Soledar's status disputed
There was still uncertainty about the fate of Soledar, a salt mining outpost that Russia claimed to have captured, against denials from Ukraine.
Both sides have conceded heavy losses in the battle for the town.
Ukraine's military governor in the embattled eastern region of Donetsk insisted Saturday that “Soledar is controlled by Ukrainian authorities, our military controls it.”
The “battles continue in and outside of the city”, he added.
He was responding to claims by Russia's defence ministry on Friday that it had “completed the liberation” of Soledar the previous day.
The industrial town with a pre-war population of about 10,000 has now been reduced to rubble through intense fighting.
Capturing Soledar could improve the position of Russian forces as they push towards what has been their main target since October -- the nearby transport crossroads of Bakhmut.