Russia says it has destroyed dozens of missiles and drones fired at its territory from Ukraine. Local officials reported two people, including a child, were killed in the attack.
The Russian defence ministry said 13 missiles and 32 drones were shot down over several Russian regions.
A child was reported killed in Bryansk region, while a man in Belgorod region was also said to have died.
The attacks follow strikes on Ukraine which killed at least 37 people.
More than 160 people were injured as Russia hit cities with missiles and drone strikes across the country on Friday - including the capital Kyiv, Odesa, Dnipro, Kharkiv and Lviv.
In an update on Saturday, Mayor of Kyiv Vitali Klitchsko said seven more bodies had been pulled from the rubble of a warehouse that had been hit - taking the total number of killed in the city to 16.
He described Friday's attacks as the deadliest for civilians in the capital, declaring a day of mourning would be held in Kyiv on Monday.
An initial statement from the Russian defence ministry said 13 missiles were destroyed over Belgorod overnight. Later, it said 32 drones had been shot down overnight in the Bryansk, Oryol, Kursk and Moscow regions.
The governor of Bryansk region, Alexander Bogomaz, said two villages were targeted and a child, born in 2014, had been killed.
A man was killed in Belgorod after a house was hit, regional Governor Vyacheslav Gladkov said. He added that four people were being treated for injuries and the water supply in the city of Belgorod was disrupted.
Ukrainian media is reporting that more than 70 drones were used in the strikes and only military targets were attacked, according to sources from Ukraine's intelligence services.
The reports say explosions were heard in regions including Moscow, Belgorod, Tula and Tver, while in Bryansk a group of drones successfully hit a electronic factory used to make Russian military equipment like long-range missiles and anti-aircraft systems.
The attacks come after what Kyiv described as Russia's biggest missile bombardment of the war so far against Ukraine.
Belgorod city is 80km (50 miles) north of the Ukrainian city of Kharkiv, which came under heavy fire by Russian forces on Friday morning as part of the wide-ranging strikes.
On Friday evening, an emergency meeting of the UN Security Council overwhelmingly condemned Russia's renewed mass-bombing campaign in Ukraine and said attacks must stop "immediately".
Countries including the US, UK and France said hitting civilian infrastructure had violated the international rules of war.
"Rather than peace, Putin chose to mark this holiday season... with an unprecedented number of drone and missile attacks," US representative to the UN John Kelley said.
Russia said Ukrainian air defences were to blame for causing damage to civilian buildings.
