Russian missile strikes killed at least six postal workers and wounded 17 others Saturday when they hit a mail depot in Ukraine's northeastern Kharkiv region, officials said.

President Volodymyr Zelensky shared a video on social media of what appeared to be a heavily damaged warehouse surrounded by rubble and a container with the logo of the Ukrainian postal operator Nova Poshta.

The six killed in the attack were all workers at the Nova Poshta depot, located in the village of Korotych on the outskirts of Kharkiv city, regional governor Oleg Sinegubov said.

"The victims, aged between 19 and 42, received shrapnel wounds and blast injuries," he said.

Of the injured being treated in hospital, seven were in a serious condition, Sinegubov said, adding that "Doctors are fighting for their lives".

The regional prosecutor's office later updated the number of injured to 17.

Sergiy Nozhka, who works for Nova Poshta, described the condition of some his colleagues as "mild to moderate severity", adding that "there are some people in a very serious condition".

He said that a rocket "flew into the neighbouring depot, but at ours too -- the windows and shutters flew out. This is not the first time".

According to the prosecutor's office, Russian forces in the Belgorod region north of Kharkiv fired S-300 missiles, two of which hit the warehouse.

"Debris analysis continues at the site in order to establish the exact number of injured and dead," office spokesman Dmytro Chubenko told Ukraine's state broadcaster Suspilne.

Separate Russian attacks on villages near the war-battered Ukrainian city of Bakhmut killed at least two people on Sunday, officials said.

Both Kyiv and Moscow are preparing for a gruelling winter ahead, as Ukraine warns of renewed strikes on its energy infrastructure and Russia contends with a Ukrainian counteroffensive to regain territory.

bur-cad/giv