Russia launched a fresh wave of missile attacks against Ukraine’s second-largest city on Sunday, just hours after Moscow accused Kyiv of pounding Russian border areas and killing civilians.

At least 28 civilians were injured after Moscow hit Ukraine’s northeastern city of Kharkiv overnight with six missiles and Iranian-made Shahed drones, regional governor Oleh Syniehubov said on Telegram. The attack, which officials said injured two children, hit cafés, residential buildings, offices and Kharkiv’s Palace hotel, according to footage circulated on social media and the city’s Mayor Ihor Terekhov.

“On New Year’s Eve, the Russians want to intimidate our city, but we are not scared — we are invincible,” Terekhov said.

Russia’s defense ministry said the strikes were aimed at “decision-making centers and military facilities” in Kharkiv, and claimed without evidence that Ukrainian military officials and 200 foreign mercenaries were holed up in the hotel complex. POLITICO couldn’t independently verify the Ukrainian or Russian statements.

Sunday’s attack comes after Russia vowed to retaliate following air strikes on its border city of Belgorod the day before, which Moscow said killed 24 people and injured 108 others in what would be the deadliest attack on Russia soil since Moscow launched its full-scale invasion of Ukraine nearly two years ago.

Kyiv hasn’t officially taken responsibility for the strikes but likely directed the fire against Russia in response to an 18-hour aerial barrage of Russian strikes across Ukraine last week that killed at least 41 civilians, local media reported citing unnamed sources.

Moscow convened a meeting of the U.N. Security Council after the Belgorod attack, while Russian Foreign Minister Sergey Lavrov on Sunday said in an interview with state-run media that Russian courts had sentenced more than 200 Ukrainian fighters to prison since the beginning of the conflict.