Russia has made minor advances in some areas since shifting its focus to fully occupying the Donbas, the UK's Ministry of Defence tweeted in a regular bulletin on Monday.
"Without sufficient logistical and combat support enablers in place, Russia has yet to achieve a significant breakthrough," it said.
Ukraine's defence of Mariupol has also exhausted many Russian units and reduced their combat effectiveness, British military intelligence said.
Reuters could not immediately verify the report.
