Vladimir Putin has vowed to "intensify" attacks against Ukraine in retaliation to an offensive on the Russian city of Belgorod which left 24 people dead.
The Russian president described the attack as "a terrorist act" during a visit to a military hospital to mark the new year.
Putin said his country would hit “military installations” in response to the Belgorod attack.
He said: "We are doing that today, and tomorrow we will continue doing it."
Vladimir Putin has vowed to 'intensify' attacks against Ukraine in retaliation to an offensive on the Russian city of Belgorod which left 24 people deadReuters"We’re going to intensify the strikes, no crime against civilians will rest unpunished, that’s for certain," he added.
Ukraine has not claimed responsibility for the attack on December 30 close to the Ukrainian border.
Other assaults including long-range suicide drones have also struck cities, but these have never been acknowledged by Kyiv.
In response, Russia launched almost 90 kamikaze drones against Ukraine, in an 11-hour onslaught in hours leading into New Year's Day.
LATEST DEVELOPMENTS:
According to the Ukrainian Air Force, it shot down 51 Iranian-made drones.
Russia launched another 35 attack drones at Ukraine in the early hours of Monday, Ukraine's air force said, with air defence systems destroying all the drones.
Gennadiy Trukhanov, the mayor of Odesa, said: "They say that how you welcome the new year is how you will live the year.
"Well, this year Ukraine will break this rule: we will persevere and we will win."
Putin said his country would hit 'military installations' in response to the Belgorod attack
ReutersIn Lviv, drones targeted two buildings associated with prominent Ukrainian nationalists.
Belgorod governor Vyacheslav Gladkov said that the death toll had risen to 25 following the death of a young child who was seriously injured in the attack.
Gladkov wrote on the Telegram messaging app: "Today, a 4-year-old girl died in a regional children's hospital. She was in a highly serious condition with combined injuries to the chest and internal organs."