MOSCOW (Reuters) - Russia said on Wednesday that it had struck the command headquarters of the Ukrainian army's southern grouping, which is based in the port of Odesa where Kyiv reported a missile attack had killed three people.

"The headquarters of the operational command of the Southern grouping of the Armed Forces of Ukraine was struck by operational and tactical aviation, missile forces and artillery," Russia's defence ministry said.

It gave no further details about the attack but said that Russian forces were improving their positions along the entire front line.

Ukrainian prosecutors said residential buildings and civilian infrastructure were damaged in Odesa in an overnight strike while the Southern military command said administrative and residential buildings, medical and educational institutions were hit.

Reuters could not independently confirm the battlefield accounts from either side.

Odesa has been a frequent target of Russian forces in the more than two-year-old war, with many attacks aimed at the city's port facilities.

(Reporting by Reuters; Writing by Maxim Rodionov; editing by Guy Faulconbridge and Christina Fincher)