Russian President Vladimir Putin made a rare trip Monday to Moscow's ally Belarus as his forces pursued their campaign to bombard Ukraine from the air amid a broad battlefield stalemate almost 10 months into the war.

Putin’s visit to Minsk came hours after Russia’s latest drone attack on Ukraine. Moscow has been targeting Ukraine’s power grid since October as part of a strategy to deprive the country of heat and power during winter.

His brief trip could herald more military support for the Kremlin war effort, after Belarus provided Russia with a launching pad for the invasion of Ukraine last February.

Putin said he and Belarus President Alexander Lukashenko discussed forming “a single defense space” in the region but rejected claims that Moscow was poised to swallow its neighbor.

“Russia isn’t interested in any kind of merger, it’s not feasible,” Putin said.

Putin said that he supported Lukashenko’s proposal to train the crews of Belarusian warplanes that already have been modified for using special warheads — a reference to nuclear weapons.

Earlier this year, Russia and Belarus have announced a plan to modernize Belarusian aircraft to make them nuclear-capable. Lukashenko said Belarusian crews have been training with Russia to operate those planes modified to carry nuclear weapons.

Lukashenko thanked Putin for providing his military with Iskander short range missiles and S-400 air defense systems. He also said the countries agreed to continue hold joint military exercises.

Read more: Kyiv targeted in early morning drone attack: Authorities

Belarus is believed to have Soviet-era weapons stockpiles that could be useful for Moscow. Lukashenko, meanwhile, needs help with his country’s ailing economy. It was a rare trip to Minsk by Putin, who usually receives Lukashenko in Russia.

Moscow has kept up its war effort despite Western sanctions and the supply of Western air defense systems to Ukrainian forces.

Sitting beside Lukashenko, Putin emphasized their close military-technical ties. He said they include not only mutual supplies of equipment but also joint work in high-tech military industries.

Analysts say the Kremlin might be seeking some kind of Belarusian military support for its Ukraine operations. But the winter weather and Russia’s depleted resources mean any big Russian attack probably won’t come soon, according to the Institute for the Study of War, a think tank in Washington.

“The capacity of the Russian military, even reinforced by elements of the Belarusian armed forces, to prepare and conduct effective large-scale mechanized offensive operations in the next few months remains questionable,” it said in an assessment published Sunday.

It concluded that “it is unlikely that Lukashenko will commit the Belarusian military (which would also have to be re-equipped) to the invasion of Ukraine.”

In Ukraine, multiple explosive drones attacked the capital before dawn. The attack came three days after what Ukrainian officials described as one of Russia's biggest assaults on Kyiv since the war started.

Russia launched 23 self-exploding drones over Kyiv while the city slept, but Ukrainian forces shot down 18 of them, the Kyiv city administration said on Telegram. No major casualties were reported from the attack, although the Ukrainian president’s office said the war killed at least three civilians and wounded 11 elsewhere in the country between Sunday and Monday.

The drone barrage caused emergency power outages in 11 central and eastern regions, including the capital region, authorities said.

Read more: Dead boy pulled from rubble of latest Russian hit on Ukraine

Monday was St. Nicholas Day, which marks the start of the Christmas holidays in Ukraine and is when children typically receive their first gifts hidden under pillows.

“This is how Russians congratulated our children on the holiday,” Serhii Kruk, the head of Ukraine's State Emergency Service, wrote on Telegram, attaching photos of firefighters at a stricken infrastructure facility.

“In the night when everyone is waiting for a miracle, the terrorist country continues to terrorize the peaceful Ukrainian people,” said Ukraine’s human rights chief, Dmytro Lubinets.

Ukrainian President Volodymyr Zelenskyy pleaded for Western countries to send sophisticated air defense systems as winter tightens its grip.

“A 100% air defense shield for Ukraine will be one of the most successful steps against Russian aggression,” Zelenskyy said by video link at a northern European regional threat conference in Latvia. “This step is needed right now.”

Wreckage from the downed drones damaged a road in the Solomianskyi district and broke windows in a multistory building in the Shevchenkyvskyi district of Kyiv, city officials said.

One drone hit the home of Olha and Ivan Kobzarenko, ages 84 and 83, in the outskirts of the capital. Ivan sustained a head injury.

Their garage was destroyed and their dog, Malysh, was killed. Olha, speaking in her bedroom where shattered glass and blood covered the floor, said the blast flung the front gate into the house.

“I know that I am not alone,” she said. “Everyone is suffering. Everyone.”

Nina Sobol, a 59-year-old clerk at one of Kyiv’s power companies, was going to work when the strikes happened. Like many of her colleagues, she waited outside while emergency services inspected damage.

“I feel really anxious," she said. "Anxious because you never know at which moment there will be an incoming missile.”

Ukraine's air force said on Telegram that its personnel were able to destroy 30 of at least 35 self-exploding drones that Russia launched across the country from the eastern side of the Azov Sea on Ukraine's southeast coast. Russia is on the other side of the sea.

The Ukrainian military has reported increasing success in shooting down incoming Russian missiles and drones, but Zelenskyy said Moscow had received a fresh batch of drones from Iran.

Meanwhile, warships from Russia’s Pacific Fleet set off Monday for joint naval drills with China. The exercise follows a series of joint maneuvers that have highlighted growing military cooperation between Moscow and Beijing as they both face tensions with the United States.

Russian Foreign Ministry spokeswoman Maria Zakharova said the U.S. was treading on dangerous ground by getting involved in the war in Ukraine.

“This dangerous and shortsighted policy has put the U.S. and Russia on the brink of a direct confrontation,” Zakharova said in a statement Monday. “Moscow is calling on Joe Biden’s administration to soberly assess the situation and refrain from dangerous escalation.”

At the United Nations, Secretary-General Antonio Guterres said he sees no prospect of talks to end the war in the immediate future.

“I strongly hope that in 2023, we’ll be able to reach peace in Ukraine,” Guterres said.