Ukraine's defense minister has stressed his country's determination to fight off Russia's invasion amid alarm about a possible major Russian offensive in February.

Oleksii Reznikov made the remark at a news conference on Sunday.

He said Ukrainians expect a possible Russian offensive in February, which will possibly be carried out for a symbolic reason around the first anniversary of its invasion, not based on a logical military view.

He said Russia is not ready for the action but it will do it anyway.

The defense minister added that not all of the Western weapons will arrive in his country in time, but expressed Ukrainians' readiness to hold back Russian forces.

US think-tank the Institute for the Study of War says Russia is concentrating troops and military equipment to stage a decisive offensive on the western Luhansk region and Bakhmut areas.

Russia on Sunday fired two missiles into the center of Ukraine's eastern region of Kharkiv, one of which hit a residential block. Kharkiv's governor said the assault injured multiple people.

Russia's military also continues its intensified offensive to seize the Ukrainian stronghold of Bakhmut in the east.