Long-range Russian bombardment killed at least 10 civilians and wounded 20 others in several parts of Ukraine on Friday, officials in Kyiv said, as a Kremlin official boasted that its forces were prepared to repel an expected Ukrainian counteroffensive this spring.

Five people died in Kostiantynivka, in eastern Ukraine’s Donetsk province, when a Russian missile hit an aid station. Ukrainian authorities last year established hundreds of “points of invincibility,” where residents hard-pressed by the war could warm up, recharge their cellphones and get food.

Prosecutors said the Russians attacked with S-300 anti-aircraft missiles. The civilians who died were refugees, according to Donetsk Gov. Pavlo Kyrylenko.

As the mostly artillery war of the winter months stretches into its second spring, Russian forces also used air-launched missiles, exploding drones and gliding bombs to attack several regions, Ukrainian air force spokesman Yurii Ihnat said.

Two civilians were killed and nine were wounded in the town of Bilopillia in Sumy province by an overnight rocket and artillery barrage and airstrikes, officials in the northeastern region said.

In southern Ukraine, Russian shelling killed one person in the city of Kherson and killed another person and wounded four others in the town of Bilozerka. President Volodymyr Zelenskyy visited that region Thursday.

Ukrainian forces are poised to use the arrival of warmer weather and new weapons from the West, including tanks, for a counteroffensive aimed at dislodging Russian troops from occupied areas.

But Dmitry Medvedev, Russia’s former president and now deputy head of the country’s Security Council chaired by President Vladimir Putin, said its forces were ready to repel a counterattack.

He added that any Ukrainian attempt to seize Crimea, which Russia illegally annexed in 2014, could trigger a nuclear response from Moscow.