Images published by Governor Sergiy Lysak showed a bus with a hole punctured through its ceiling and what appeared to be blood and shattered glass scattered across its floors.

"The enemy attack took nine lives," Lysak wrote on Telegram.

The bus was in Marganets, a city of 45,000 people around 10 kilometres (six miles) from the front line, he said.

"The number of wounded is constantly growing. As of now, there are 30 of them," he added.

Ukrainian authorities also reported fires in several regions overnight after Russian attacks.

Strikes were reported in the regions of Kyiv, Kharkiv, Poltava and Odesa.

Russia launched over 100 drones at Ukraine between Tuesday evening and early Wednesday, the Ukrainian air force said.

In Russia, one person was reported wounded by Ukrainian shelling in the Belgorod region.

Russia's invasion, which began in February 2022, has resulted in tens of thousands of deaths and spurred the biggest crisis in relations between Moscow and the West since the Cold War.

Ukraine peace talks involving international foreign ministers scheduled to take place in London on Wednesday were postponed.